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Primary Intrarenal Lipoma of Surgical Significance1
PRIMARY INTRARENAL LIPOMA OF SURGICAL SIGNIFICANCE 1 THOMAS D. ROBERTSON
(BY INVITATION) AND
JOHN R. HAND
From the Portland Clinic, Portland, Oregon
A review of the literature reveals primary intrarenal lipoma of significant size removed surgically to be a rare lesion. Twelve such cases have come to our attention. Two additional cases are reported herein. Smaller, nonclinical intrarenal lipomas are much more frequent. In a report from the Mayo Clinic it is stated that 14 small, intrarenal lipomas were found at autopsy. Most of these were cortical and subcapsular fatty nodules. In our experience they occur in about 1 per cent of all autopsies. The kidney itself normally does not contain fat. Hence, the pathogenesis of intrarenal lipomas is interesting. Two principal theories of the origin of these tumors have been entertained: (1) Alsberg, quoted by Lower and Belcher, believed that these tumors have their origin in embryonal rests of fat. (2) More generally, however, it is thought that they arise from multiplication of perivascular and intertubular connective tissue cells which undergo fatty metamorphosis. It is our opinion that embryonal fatty tissue may possibly be carried into the cortex of the kidney by the collecting tubules which extend up toward the capsule to unite with the convoluted tubules. This is illustrated in figure 1. The smooth muscle found in intrarenal lipoma is thought to arise from the muscle tissue of the blood vessels. Myxomatous connective tissue present in such tumors indicates active growth and is a step toward malignancy. It is also thought that cortical and subcortical tumors may originate from the pelvic region, or from the junction of the medulla and the cortex, and push their way outward along the path of least resistance to reach a cortical position. It has been noted, too, that these tumors sometimes occur in the presence of lipoma elsewhere. Intrarenal lipoma should not be confused with perirenal lipoma. Perirenal lipomas of 2 main types. One type may exist as an encapsulated tumor impinging upon the extrarenal aspect of the kidney and often displacing it medially. This type is prone to recurrence after surgical 1 Read at nineteenth annual convention, Western Section, American Urological Association, Del Monte, Calif. May 1-3, 1941. 458
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removal and to malignant transformation. The second type may be more diffuse and entirely surround the kidney. This type sometimes presses upon the renal blood supply to such an extent that kidney atrophy may occur. Perirenal tumors are unilateral, and must not be confused with hypertrophy of the fatty capsule of the kidney, which is bilateral and occurs in obesity. Lipoma-like overgrowth of fat may occur about the kidney and about the pelvis in various diseases of the kidney which lead to atrophy of that organ. Also, a pyonephrotic shell of kidney may be filled by fat in a condition called "replacement lipomatosis." The case of intrarenal lipoma reported by Pemberton and McCaughan might
FIG. L Section through embryonal kidney. a Embryonic connective tissue; b collecting tubules. Embryonic connective tissue has potentiality of developing into fatty tissue.
easily have been mistaken for a perirenal lipoma of the encapsulated They demonstrated the capsule of the kidney to be continuous over the tumor. From a clinical standpoint such a tumor might better be con sidered a perirenal lipoma since it is not apt to be confused with a clear cell primary renal carcinoma as in the case of a true intrarenal lipoma. The latter at times impinges upon the pelvis and gives the roentgenographic picture of a primary renal carcinoma such as occurred in our cases. Hematuria may also exist, and is more frequent in the true intrarenal further confusing the picture with a renal carcinoma. Case 1. Mrs. E. B., aged 29, white, entered St. Vincent's hospital on December 15, 1932 complaining of severe pain in the left side and radiating down the left ureter into the bladder. This pain began acutely the same morning
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and became continuous. It was accompanied by nausea and vom1tmg. Definite tenderness was present over the left kidney area. Severe pain was elicited on deep pressure. The entire abdomen was intermittently rigid, and pain was elicited by pressure over any area. Cystoscopic examination showed the bladder to be normal. Ureteral catheterization disclosed 3 plus red blood cells in the urine from the left kidney and 1 plus in that from the right kidney. Phthalein appeared in less than 4 minutes from either side. The pyelogram on the right side was essentially normal. That on the left suggested a renal tumor (fig. 2). The lower border of the left kidney was indistinct and appeared to be
FIG. 2. Left pyelogram showing deformity associated with benign intrarenal lipoma. An elongated isthmus to upper major calyx may be seen leading to the dilated, deformed minor calyces. Note the smooth "C" shaped deformity involving lateral aspect of upper major calyx and upper surface of middle calyx.
at the level of the transverse process of the faird lumbar vertebra. The kidney appeared to be markedly enlarged. Its outline was smooth and regular. The pelvis was filled well. The isthmus to the upper major calyx was elongated and presented a so-called "spider-leg" deformity. Its minor calyces were blunted. Exploration revealed extensive hemorrhage about the capsule of the left kidney. During mobilization of this kidney, which appeared to be about 3 times normal size, a lipoma partly shelled out. Pathologic examination disclosed the following: The kidney weighed 476 gm. Bulging from its anterior superior two-thirds was a tumor mass measuring 10 by 11 by 9 cm. The tumor was covered by a
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capsule which was continuous over the kidney. Most of the capsule had been torn from the kidney. The tumor mass had the consistency of normal liver, and on cut section the surfaces presented a mottled, indefinitely lobulated, glistening, yellow to pink, streaked-red appearance. It shelled out easily from the kidney, having partly shelled out at operation, and there was clotted blood at the line of cleavage. It had impinged on the anterior aspect of the pelvis which accounted for the appearance of the pyelogram. Careful examination of the veins at the hilus disclosed no tumor invasion. A line of demarcation was seen between the periphery of the tumor and the adjacent renal parenchyma with no capsule demonstrable. The tumor tissue appeared
FIG.
3. Section of gross tumor.
a Fatty tissue; b layer of renal tissue; c isolated lipoma.
to be invading the kidney tissue, but did not penetrate deeply. Adjacent to this tumor was a smaller, soft, subcapsular tumor, 2 cm. in diameter. The smaller tumor elevated the capsule slightly, and had the yellow, greasy, glistening appearance and consistency of fatty tissue. It was not connected with the larger tumor. This can he seen in figures 3 and 4. Microscopic Examination: The larger tumor (figs. 5 and 6) showed variable proportions pf well differentiated fat, characterized by large fat globules distending the ~ell in the usual manner and surrounded by a thin cell membrane adjacent to *hich was a small, compressed nucleus. Quite a number of fairly la;ge blood !vessels coursed throughout this tumor. Accompanying these vessels were µbrils which did not stain red by Van Gieson's stain. Along these fibrils were ovoid and round nuclei, and among the fibrils were many poly-
FrG. 4. Low power view of subcapsular lipoma. tissue without any capsule.
Note how lipoma rests on adjacent kidney
FIG. 5. Low power view showing adult fatty tissue with fibrous connective septa which carry abundant blood vessels and sinusoid pools of blood. 462
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hedral-shaped cells containing various sized small vacuoles and central round nuclei. The nuclei of these cells varied somewhat in size and shape, but no mitotic figures were encountered. These cells had the appearance of embryonal fat cells and smooth muscle. The smaller tumor was composed entirely of well differentiated fat cells, as described above. Neither of these tumors had a capsule, and fat cells lay immediately adjacent to renal parenchyma and stroma which was somewhat compressed by the tumors.
Frc. 6. High power view showing adult fat cells; nuclei compressed to side; embryonaJ fat cells, foamy in appearance with central nuclei; connective tissue; and blood vessels. a Adult fat cell; b blood vessel; c embryonal fat cells; d fibrous tissue.
Case 2. Mrs. N. S. came to the Portland Clinic on January 21, 1938 for relief of recurring attacks of right upper quadrant pain and constipation. She was 48 years of age. She had had a salpingectomy for tubal pregnancy, an appendectomy in 1918 and a hemorrhoidectomy in 1924. During the 3 years before admission she had experienced 3 major attacks of knife-like right upper quadrant pain which radiated through to the back and to the tip of the right shoulder blade. The first attack was associated with questionable jaundice. The last attack, on January 1, 1938, persisted for 3 days and was associated with fever. Since the onset of the attacks the patient had been unable to tolerate fats and cabbage. Her bowel function had been impaired, and re-
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quired the use of laxatives. Her weight had been stationary at 166 pounds for 10 years. On physical examination she was found to be short and stocky. Her skin was dry and showed a moderate amount of generalized subcutaneous fat. Blood pressure was 130 systolic and 85 diastolic. The abdomen was fairly obese. Slight tenderness was elicited over the gall-bladder area. In the left renal area there was a suggestion of possible enlargement of the kidney. The remainder of the examination showed no noteworthy changes.
FIG. 7. Retrograde pyelogram showing elongation and flattening of pelvis with absence of filling in upper major calyx.
Blood and urine examinations were within normal limits. Blood Kolmer was negative. Renal function test, using phthalein, was normal. Roentgen ray examination of the kidney, ureteral, and bladder areas was negative for lithiasis. The left renal shadow was enlarged. On cystoscopic examination, January 27, there was a moderate cicatricial urethritis with an associated mild trigonitis. The bladder was otherwise clean. Each meatus appeared normal, and clear urine came from each one. The urine from the left meatus came at infrequent intervals. Urine specimens from either side were negative for any evidence of infection. A retrograde pyelogram (fig. 7) showed the left pelvis to be elongated and depressed laterally and downward so that it rested at right angles to the ureter. The minor calyces from the middle
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major calyx were effaced, while the inferior major and minor calyces were normal, The upper major calyces did not fill. The ureter was normal throughout. The right pyelogram showed a normal pelvis, calyces and ureter. An intravenous urogram showed a dilated upper major calyx of the left kidney with the isthmus not outlined (fig. 8). Slight filling occurred in the minor calyces of the middle and inferior calyces. A diagnosis of (1) left renal tumor and (2) chronic cholecystitis with stones was made. On January 28, 1938 the left kidney was exposed through a left Mayo inc1s10n. The kidney was definitely enlarged; and fatty, elevated, circumscribed,
FIG. 8. Intravenous urogram demonstrating filling of upper major calyx which is dilated 4.
dome shaped areas arose from its surface. When the kidney was delivered a large lipoma was enucleated from its upper pole. A left nephrectomy was done. The pathologic examination showed the following: The kidney weighed 281.4 gm., and was 14 cm. long. The lower pole was somewhat pointed while the upper pole was enlarged by a tumor mass which bulged both laterally and medially. Here the kidney reached a maximum width of 12 cm. and a thickness of 5 cm. The nodule bulging in the lateral aspect of the upper pole, somewhat superiorly, had a basal diameter of 7 cm. and a thickness of 4 cm. It bulged 4 cm. above the surface of the kidney, and was covered by renal capsule. This portion was partially shelled out because
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of rupture of the capsule, and the major portion was detached. The tissue thus exposed was yellow and greasy, rather homogeneous in appearance, looked like fat, and floated in fluid. On cutting the kidney sagittally it was seen that there was a fatlike tissue continuous posteriorly in the region of the hilus and over the medial aspect to form a bulging area which was friable where the capsule was torn. The basal diameter of this area was 4.5 cm. The tissue here was mottled red to gray to yellow in appearance in contrast to the homogeneous yellow appearance of the lateral aspect. This yellow, fatlike tumor continued
FIG. 9. Gross specimen of kidney showing multiple intrarenal lipomas, largest arising from upper pole.
into the hilar fat from which it could not be differentiated, there being no capsule separating it from this fat. It also continued posteriorly as a knob bulging from the lower third of the kidney. The center of this bulging area was located 5 cm. from the lower pole, and had a basal diameter of 3.5 cm. and a width of 3 cm. It bulged 1.5 cm. above the surface of the kidney. It was continuous with the main tumor mass described above. Other extensions of the tumor were seen as in the illustrations (figs. 9 and 10). There was no grossly visible capsule separating the tumor from the renal parenchyma. In
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FIG. 10. Sagittal section showing irregular lobulation of fat throughout upper two.thirds of kidney.
FIG. lL Low power view showing adult fat cells, marked vascularity of tumor, and absence of capsule between fatty tumor and renal parenchyma.. a Adu] t fat cell; b blood vessels.
FIG. 12.
Low power view showing cellular, vascular connective tissue mixed with fat
FIG. 13. High power view showing a vascular connective tissue, b adult fat cells, and c embryonal fat. 468
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the upper pole the calyces were elongated and the renal papillae flattened to give the "spider-leg" deformity seen in the roentgenogram. Microscopic Examination: Some portions of the tumor consisted entirely of adult fat cells (figs. 11 and 12). Throughout this fatty tumor there were branching blood vessels which were rather thick-walled structures. In some places considerable connective tissue with collagen fibrils accompanied these blood vessels (fig. 13). In the soft, reddish portion, which was separate, the tumor was composed principally of connective tissue and blood vessels so that in places it looked almost like an hemangioma of the cavernous type. However, one could still see fat cells scattered throughout even in this more vascular area. There was no distinct capsule about any of the tumor tissue. The fat cells lay adjacent to the renal parenchyma and stroma. The blood vessels seemed to be coming out along the border into the substance of the tumor. There were no blood vessels invaded by tumor cells. The kidney parenchyma was essentially unchanged, excepting for replacement and impingement by tumor tissue.
Details of symptoms and pathology of cases collected from the literature. 1. Grawitz: No symptoms given. Pathology: A large tumor, weighing together with the kidney 2,200 gm. and measuring 23 by 19 by 12 cm., extended from the hilus to the cortex of the kidney. It was situated inside the renal capsule. Its main constituent was fat. There was a fibrous compression capsule composed of kidney tissue about it. Some parts of the growth gave the appearance of an arterial angioma with much smooth muscle, these areas appearing like myoma, but even here fat lobules were present. 2, Alsberg: Symptoms: Pelvic pain. Large, freely movable tumor, the size of a child's head, was located in the region of the right kidney. Pathology: There were multiple lipomas varying from the size of a millet seed to that of a waL,ut with one small adrenal rest. The tumors were scattered evenly through the organ, both in the cortex and medullary areas. Large nodules sharply delineated from the kidney substance, and could be easily enudeated. Microscopically many of these tumors consisted of pure fat, while in the others there was abundant fibrous tissue. Some areas showed an appearance suggestive of spindle cell sarcoma with overgrowth of vessels. 3. Warthin: Tumor discovered at childbirth, which required instrumental delivery. Pathology: The kidney and tumor weighed 908 gm. and measured 14 by 8 by 6 cm. The tumor extended, cordlike, into the upper end of the ureter for 6 inches in length, with the diameter of
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this area 1 inch. This extension was smooth and blunt below. It was unattached to the ureteral wall, and there was complete filling of the lumen. The pelvis was dilated, and completely filled by tumor. There was some mucinous degeneration. The tumor was well differentiated. 4. Bartsch: Symptoms: Increase in size of abdomen for 6 years, pain while walking for 3 weeks, frequency for 2 years, no hematuria. Right
1.01s qm 12
Fm. 14. Schematic drawings, from authors' descriptions, of intrarenal lipomas removed surgically.
abdominal mass. Pathology: The kidney and tumor weighed 2,250 gm. and measured 19 by 12 by 25 cm. The tumor separated the 2 poles of the kidney. It was composed mostly of pure fat. The rest was vascular and fibrous, with smooth muscle around the vessels. There was a capsule present in some places, and in other areas fatty tumor tissue lay directly against the kidney tissue. The calyces were compressed the tumor. 5. Keenan and Archibald: Symptoms: Attacks of dull pain in the right side, lump in the right side. Pathology: The kidney weighed
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350 gm., including the tumor. The tumor itself measured 4.7 cm. in diameter, with the kidney measuring 9.5 by 8.5 by 5.7 cm. The tumor was sharply demarcated from the surrounding kidney tissue, and occupied the center of the convexity. It appeared to divide the kidney poles transversely and longitudinally underneath the capsule. The pelvis was unchanged excepting by the dilatation. The tumor was globular on cut section, with an indefinite capsule. At the center the tumor appeared to consist of ordinary fat without lobulation. This shaded off to a more friable zone of grayish color which showed considerable reddish-brown mottling, giving the impression that it was stained by extravasated blood. Two small fatty looking areas, about 3 cm. in diameter, were present deep in the kidney in the upper pole, separated from the larger tumor. They had no capsule. Microscopically the tumor was mainly thick walled, and surrounded by what appeared on superficial examination to be young fibrous tissue, while here and there, though mainly at the periphery, there were small areas of large, irregularly shaped, fatcontaining cells of indeterminate type. A section of this tumor was not available. There was a question in our minds whether this was really a lipoma, but a detailed discussion seems to leave little doubt that it was . 6. Hinz: Symptoms: Colicky, right upper quadrant pain. On examination the right upper abdomen was found to be rigid, and a diagnosis of chol.ecystitis with stones was made. The gall-bladder on exploration was found to be normal. But a large mass was noted in the region of the right kidney. Cystoscopic examination on the table showed the kidney to be normal. The patient was then turned over, and a right nephrectomy was performed. It was noted that hemorrhage had occurred about the kidney. Pathology: The kidney was 12 cm. long. After stripping the capsule, needlehead to pea sized nodules could be seen irregularly distributed over the surface of the kidney. These were attached to the capsule, but had not broken through. In cross section it was noted that 1 large tumor extended to the kidney pelvis. All the nodules were surrounded by normal kidney tissue. Microscopic diagnosis was myolipoma. 7. Lower and Belcher. Symptoms: Pain, indigestion, nervousness of 11 months' duration, loss of 12 pounds in weight during the month before admission, mass in the left kidney region. Pyelogram showed deformity of the left pelvis strongly suggestive of new growth. Patient was rather emaciated. Pathology: In the middle of the kidney, on the lateral surface, there was an almost globular, subcapsular mass, 4 inches in diame-
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ter, fairly well encapsulated, and compressing the pelvis. It weighed 420 gm. The renal vessels were not involved. Microscopically fat and fibrous tissue with no true capsule was noted. 8. Hunt and Simon: Symptoms: For 2 years distress in the right lumbar region, severe for 2 months. Hematuria for 10 days, becoming marked. Urgency, frequency, dysuria, loss of 10 pounds in 1 month, and anemia. Pyelogram showed the lower calyx to be slightly dilated, and the minor calyx to be elongated. Pathology: Tumor 2.5 cm. in diameter on the anterior surface of the kidney. It could not be enucleated at operation. The yellow tumor extended down to the pelvis. It was not encapsulated, but was sharply demarcated. Microscopically it showed adult fat with many vascular channels surrounded by islands of moderately dense fibrous tissue. Fibrous tissue comprised about onethird of the total volume. Occasional myxomatous areas were noted. 9. Nicholson and Gillespie. Symptoms: Severe abdominal pain in the right side and hematuria of 3 days' duration. Blood pressure was 280/140. There was tenderness in the right kidney region. Cystoscopic examination showed blood coming from the right meatus. Pyelograms showed deformity of the right pelvis. A diagnosis was made of intrarenal hemorrhage or malignancy. On exploration a large mass, which was formed by a massive hemorrhagic infiltration, was found in the region of the right kidney. Pathology: The kidney measured 16 by 8.5 by 6.5 cm. A large hematoma was found on the upper pole of the kidney. In the upper half of the kidney there was a yellowish tumor measuring 2.6 by 3.5 by 2.5 cm., involving the medullary and cortical substance of the kidney and completely replacing it. The tumor was definitely demarcated from the kidney substance. Microscopic examination showed sections from various places in the tumor to be composed of adult adipose tissue. Diagnosis was lipoma of the kidney with partial necrosis and extensive subcapsular and intrapelvic hemorrhages. 10. Vertova: Symptoms: Pain in the right lower abdomen for 19 years, constipation, slight fever. Onset was sudden, with pain, hematuria, and albuminuria rapidly progressing to uremia. But this cleared up nicely. The urine was normal. Uroselectan showed normal calyces. The kidney was irregular in shape, and enlarged in the lower portion. Pathology: The kidney weighed 650 gm. It was ovoid, and measured 14 cm. in length, 10 cm. in width, and 6 cm. in thickness. There were many subcapsular nodules of various sizes, with the smallest the size of a grain of rice. At each pole there was a nodule the size of a walnut, and in the posterior part of the kidney there was one the size of an orange.
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The color of these nodules was grayish-yellow. Microscopically the tumor tissue was in direct contact with the kidney tissue, with no true capsule. A connective tissue capsule surrounded the smallest nodule. The tumors consisted mostly of adult fibrous connective tissue. The vessels were numerous in places. Fat appeared especially at the edge at various points. There were no glands, smooth muscle, or cartilage. 11. Pemberton and McCaughan: Syrn.ptoms: Intermittent attacks of diarrhea with generalized abdominal cramps of 12 months' duration. Tumor in the left upper quadrant. Negative intravenous urograms. Pathology: The kidney and tumor weighed 850 gm. and measured 15 by 12 by 12 cm. The tumor was attached to the lower pole of the kidney, necessitating removal of the tip of the lower pole. The kidney capsule was reflected over the tumor which did not extend deeply into the kidney. Microscopically the tumor was shown to be composed mainly of adult adipose tissue with a few embryonal fat cells. There was a scant amount of connective tissue around the blood vessels. The blood vessels to the tumor came from the kidney cortex. 12. Potter :2 Symptoms: Pain and a mass in the right side, indigestion, dizziness, headaches, nervousness, fatigue, and loss of weight. Pathology: The gross specimen was a large kidney and tumor weighing 1.015 gm. and measuring 24 by 19 by 15 cm. In the middle and posterior portions of the lateral surface there was a large, nodular, encapsulated tumor dividing the kidney both ways. The largest part of the specimen consisted of the tumor mass which was fairly well encapsulated. A few blood clots in the tumor showed central necrosis. The tumor itself was of nodular structure, yellowish in color, mottled in appearance, and of medium consistency. In intact areas of the kidney there were secondary nodules up to the size of a plumb. In the parts adjoining the tumor the kidney tissue was separated from the tumor by a small amount of coarse connective tissue which was very rich in hyperemic blood vessels. The blood vessels frequently showed marked hyaline degeneration of their walls which were exceedingly thickened. The ureter was 13 cm. long and intact. The renal pelvis was narrowed. Microscopic sections were characterized by a typical lipomatous structure which included fibrous connective tissue. SUMMARY
Twelve cases of primary intrarenal lipoma, removed surgically, have been collected from the literature. Two additional cases are presented, 2
The cases of Wells and Chevennaz, reported by Potter, could not be confirmed.
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These tumors, because of their cortical and subcortical position in kidney, may attain considerable size before giving rise to symptoms. Pain and hematuria may call attention to the presence of such a tumor at an early date. Clinically primary renal lipoma may be indistinct from primary renal carcinoma. The 2 cases reported herein were thought to be renal carcinoma. Pathologic examination, however, showed them to be benign intrarenal lipomas. This is the most important feature of these case reports, as the prognosis in the 2 conditions is decidedly different. A primary renal carcinoma of the size noted in these 2 cases would, no doubt, terminate fatally. The 2 patients whose cases we report are well today and present no evidence of recurrence. Intrarenal lipomas may contain variable amounts of connective tissue, smooth muscle, myxomatous vascular tissue, and cartilage, or they may show sarcomatous transformation (no true sarcomas of this type been reported to our knowledge). A new concept of the origin of primary intrarenal lipoma is suggested: namely, that these tumors arise from the embryonic connective tissue surrounding the developing collecting tubules. The embryonic connec, tive tissues may be pushed to a cortical or subcapsular position by the developing collecting tubule buds. We wish to express our appreciation to Dr. Herbert Thatcher and Dr, John Cheetham, of Portland, for allowing us to report Case 1. We also wish to thank Dr. Adolph A. Kutzmann, of Los Angeles, for calling our attention to the cases reported by Hinz and Nicholson and Gillespie. REFERENCES ALSBERG, A.: Case report of a lipoma of the kidney. Arch. f. klin. Chlr., 44: 458, 1892. BARTSCH, C.: Ueber einem seltenen Fall von Nierenlipom. Greisswald, 1900. GRA,VITZ, P.: Arch. f. Path. Anat. u. Physiol., 93: 39-63, 1883. HINZ, R.: Massenblutung ins Nierenlager bei Myolipom. Arch. f. klin. Chir., 132: 149-155, 1924. HUNT, VERNE C., AND SnwN, HAROLD E.: Perirenal and intrarenal lipoma. Am. J. Surg., 4: 390--395, 1928. KEENAN, C. B., AND ARCHIBALD, E. W.: Fatty tumor of kidney suggesting a metamorphosis of adrenal cells into true fat. J. Med. Research, 16: 121, 1907. LOWER, W. E., AND BELCHER, G. W.: Massive lipoma of the kidney, Surg., Gynec. and Obst, 45: 1-6, 1927. NICHOLSON, M.A., AND GILLESPIE, M. G.: Lipoma of the kidney, report of a case. J. Urol., 26: 395-403, 1931. PEMBERTON, J. DE J., AND MCCAUGHAN, J. M.: Intrarenal and perirenal lipomata, Surg,, and Obst., 66: 110--115, 1933. POTTER, ALFRED H.: Massive renallipoma, Urol. and Cu tan. Rev., 40: 717-724, 1936. VERT0VA, G.: Su di un caso di tumore benigno rare non ipemefroide del rene destro. Tumori, 6: 620-633, J.932. Abstr. Am. J. Cane., 19: 956 1933. W ARTHIN, A. S.: Fibro-lipoma of the kidney, J. Path. and Bact., 4: 404-411, 1897.
(BY INVITATION) AND
JOHN R. HAND
From the Portland Clinic, Portland, Oregon
A review of the literature reveals primary intrarenal lipoma of significant size removed surgically to be a rare lesion. Twelve such cases have come to our attention. Two additional cases are reported herein. Smaller, nonclinical intrarenal lipomas are much more frequent. In a report from the Mayo Clinic it is stated that 14 small, intrarenal lipomas were found at autopsy. Most of these were cortical and subcapsular fatty nodules. In our experience they occur in about 1 per cent of all autopsies. The kidney itself normally does not contain fat. Hence, the pathogenesis of intrarenal lipomas is interesting. Two principal theories of the origin of these tumors have been entertained: (1) Alsberg, quoted by Lower and Belcher, believed that these tumors have their origin in embryonal rests of fat. (2) More generally, however, it is thought that they arise from multiplication of perivascular and intertubular connective tissue cells which undergo fatty metamorphosis. It is our opinion that embryonal fatty tissue may possibly be carried into the cortex of the kidney by the collecting tubules which extend up toward the capsule to unite with the convoluted tubules. This is illustrated in figure 1. The smooth muscle found in intrarenal lipoma is thought to arise from the muscle tissue of the blood vessels. Myxomatous connective tissue present in such tumors indicates active growth and is a step toward malignancy. It is also thought that cortical and subcortical tumors may originate from the pelvic region, or from the junction of the medulla and the cortex, and push their way outward along the path of least resistance to reach a cortical position. It has been noted, too, that these tumors sometimes occur in the presence of lipoma elsewhere. Intrarenal lipoma should not be confused with perirenal lipoma. Perirenal lipomas of 2 main types. One type may exist as an encapsulated tumor impinging upon the extrarenal aspect of the kidney and often displacing it medially. This type is prone to recurrence after surgical 1 Read at nineteenth annual convention, Western Section, American Urological Association, Del Monte, Calif. May 1-3, 1941. 458
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removal and to malignant transformation. The second type may be more diffuse and entirely surround the kidney. This type sometimes presses upon the renal blood supply to such an extent that kidney atrophy may occur. Perirenal tumors are unilateral, and must not be confused with hypertrophy of the fatty capsule of the kidney, which is bilateral and occurs in obesity. Lipoma-like overgrowth of fat may occur about the kidney and about the pelvis in various diseases of the kidney which lead to atrophy of that organ. Also, a pyonephrotic shell of kidney may be filled by fat in a condition called "replacement lipomatosis." The case of intrarenal lipoma reported by Pemberton and McCaughan might
FIG. L Section through embryonal kidney. a Embryonic connective tissue; b collecting tubules. Embryonic connective tissue has potentiality of developing into fatty tissue.
easily have been mistaken for a perirenal lipoma of the encapsulated They demonstrated the capsule of the kidney to be continuous over the tumor. From a clinical standpoint such a tumor might better be con sidered a perirenal lipoma since it is not apt to be confused with a clear cell primary renal carcinoma as in the case of a true intrarenal lipoma. The latter at times impinges upon the pelvis and gives the roentgenographic picture of a primary renal carcinoma such as occurred in our cases. Hematuria may also exist, and is more frequent in the true intrarenal further confusing the picture with a renal carcinoma. Case 1. Mrs. E. B., aged 29, white, entered St. Vincent's hospital on December 15, 1932 complaining of severe pain in the left side and radiating down the left ureter into the bladder. This pain began acutely the same morning
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and became continuous. It was accompanied by nausea and vom1tmg. Definite tenderness was present over the left kidney area. Severe pain was elicited on deep pressure. The entire abdomen was intermittently rigid, and pain was elicited by pressure over any area. Cystoscopic examination showed the bladder to be normal. Ureteral catheterization disclosed 3 plus red blood cells in the urine from the left kidney and 1 plus in that from the right kidney. Phthalein appeared in less than 4 minutes from either side. The pyelogram on the right side was essentially normal. That on the left suggested a renal tumor (fig. 2). The lower border of the left kidney was indistinct and appeared to be
FIG. 2. Left pyelogram showing deformity associated with benign intrarenal lipoma. An elongated isthmus to upper major calyx may be seen leading to the dilated, deformed minor calyces. Note the smooth "C" shaped deformity involving lateral aspect of upper major calyx and upper surface of middle calyx.
at the level of the transverse process of the faird lumbar vertebra. The kidney appeared to be markedly enlarged. Its outline was smooth and regular. The pelvis was filled well. The isthmus to the upper major calyx was elongated and presented a so-called "spider-leg" deformity. Its minor calyces were blunted. Exploration revealed extensive hemorrhage about the capsule of the left kidney. During mobilization of this kidney, which appeared to be about 3 times normal size, a lipoma partly shelled out. Pathologic examination disclosed the following: The kidney weighed 476 gm. Bulging from its anterior superior two-thirds was a tumor mass measuring 10 by 11 by 9 cm. The tumor was covered by a
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capsule which was continuous over the kidney. Most of the capsule had been torn from the kidney. The tumor mass had the consistency of normal liver, and on cut section the surfaces presented a mottled, indefinitely lobulated, glistening, yellow to pink, streaked-red appearance. It shelled out easily from the kidney, having partly shelled out at operation, and there was clotted blood at the line of cleavage. It had impinged on the anterior aspect of the pelvis which accounted for the appearance of the pyelogram. Careful examination of the veins at the hilus disclosed no tumor invasion. A line of demarcation was seen between the periphery of the tumor and the adjacent renal parenchyma with no capsule demonstrable. The tumor tissue appeared
FIG.
3. Section of gross tumor.
a Fatty tissue; b layer of renal tissue; c isolated lipoma.
to be invading the kidney tissue, but did not penetrate deeply. Adjacent to this tumor was a smaller, soft, subcapsular tumor, 2 cm. in diameter. The smaller tumor elevated the capsule slightly, and had the yellow, greasy, glistening appearance and consistency of fatty tissue. It was not connected with the larger tumor. This can he seen in figures 3 and 4. Microscopic Examination: The larger tumor (figs. 5 and 6) showed variable proportions pf well differentiated fat, characterized by large fat globules distending the ~ell in the usual manner and surrounded by a thin cell membrane adjacent to *hich was a small, compressed nucleus. Quite a number of fairly la;ge blood !vessels coursed throughout this tumor. Accompanying these vessels were µbrils which did not stain red by Van Gieson's stain. Along these fibrils were ovoid and round nuclei, and among the fibrils were many poly-
FrG. 4. Low power view of subcapsular lipoma. tissue without any capsule.
Note how lipoma rests on adjacent kidney
FIG. 5. Low power view showing adult fatty tissue with fibrous connective septa which carry abundant blood vessels and sinusoid pools of blood. 462
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hedral-shaped cells containing various sized small vacuoles and central round nuclei. The nuclei of these cells varied somewhat in size and shape, but no mitotic figures were encountered. These cells had the appearance of embryonal fat cells and smooth muscle. The smaller tumor was composed entirely of well differentiated fat cells, as described above. Neither of these tumors had a capsule, and fat cells lay immediately adjacent to renal parenchyma and stroma which was somewhat compressed by the tumors.
Frc. 6. High power view showing adult fat cells; nuclei compressed to side; embryonaJ fat cells, foamy in appearance with central nuclei; connective tissue; and blood vessels. a Adult fat cell; b blood vessel; c embryonal fat cells; d fibrous tissue.
Case 2. Mrs. N. S. came to the Portland Clinic on January 21, 1938 for relief of recurring attacks of right upper quadrant pain and constipation. She was 48 years of age. She had had a salpingectomy for tubal pregnancy, an appendectomy in 1918 and a hemorrhoidectomy in 1924. During the 3 years before admission she had experienced 3 major attacks of knife-like right upper quadrant pain which radiated through to the back and to the tip of the right shoulder blade. The first attack was associated with questionable jaundice. The last attack, on January 1, 1938, persisted for 3 days and was associated with fever. Since the onset of the attacks the patient had been unable to tolerate fats and cabbage. Her bowel function had been impaired, and re-
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THOMAS D. ROBERTSON AND JOHN R. HAND
quired the use of laxatives. Her weight had been stationary at 166 pounds for 10 years. On physical examination she was found to be short and stocky. Her skin was dry and showed a moderate amount of generalized subcutaneous fat. Blood pressure was 130 systolic and 85 diastolic. The abdomen was fairly obese. Slight tenderness was elicited over the gall-bladder area. In the left renal area there was a suggestion of possible enlargement of the kidney. The remainder of the examination showed no noteworthy changes.
FIG. 7. Retrograde pyelogram showing elongation and flattening of pelvis with absence of filling in upper major calyx.
Blood and urine examinations were within normal limits. Blood Kolmer was negative. Renal function test, using phthalein, was normal. Roentgen ray examination of the kidney, ureteral, and bladder areas was negative for lithiasis. The left renal shadow was enlarged. On cystoscopic examination, January 27, there was a moderate cicatricial urethritis with an associated mild trigonitis. The bladder was otherwise clean. Each meatus appeared normal, and clear urine came from each one. The urine from the left meatus came at infrequent intervals. Urine specimens from either side were negative for any evidence of infection. A retrograde pyelogram (fig. 7) showed the left pelvis to be elongated and depressed laterally and downward so that it rested at right angles to the ureter. The minor calyces from the middle
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major calyx were effaced, while the inferior major and minor calyces were normal, The upper major calyces did not fill. The ureter was normal throughout. The right pyelogram showed a normal pelvis, calyces and ureter. An intravenous urogram showed a dilated upper major calyx of the left kidney with the isthmus not outlined (fig. 8). Slight filling occurred in the minor calyces of the middle and inferior calyces. A diagnosis of (1) left renal tumor and (2) chronic cholecystitis with stones was made. On January 28, 1938 the left kidney was exposed through a left Mayo inc1s10n. The kidney was definitely enlarged; and fatty, elevated, circumscribed,
FIG. 8. Intravenous urogram demonstrating filling of upper major calyx which is dilated 4.
dome shaped areas arose from its surface. When the kidney was delivered a large lipoma was enucleated from its upper pole. A left nephrectomy was done. The pathologic examination showed the following: The kidney weighed 281.4 gm., and was 14 cm. long. The lower pole was somewhat pointed while the upper pole was enlarged by a tumor mass which bulged both laterally and medially. Here the kidney reached a maximum width of 12 cm. and a thickness of 5 cm. The nodule bulging in the lateral aspect of the upper pole, somewhat superiorly, had a basal diameter of 7 cm. and a thickness of 4 cm. It bulged 4 cm. above the surface of the kidney, and was covered by renal capsule. This portion was partially shelled out because
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THOMAS D. ROBERTSON AND JOHN R. HAND
of rupture of the capsule, and the major portion was detached. The tissue thus exposed was yellow and greasy, rather homogeneous in appearance, looked like fat, and floated in fluid. On cutting the kidney sagittally it was seen that there was a fatlike tissue continuous posteriorly in the region of the hilus and over the medial aspect to form a bulging area which was friable where the capsule was torn. The basal diameter of this area was 4.5 cm. The tissue here was mottled red to gray to yellow in appearance in contrast to the homogeneous yellow appearance of the lateral aspect. This yellow, fatlike tumor continued
FIG. 9. Gross specimen of kidney showing multiple intrarenal lipomas, largest arising from upper pole.
into the hilar fat from which it could not be differentiated, there being no capsule separating it from this fat. It also continued posteriorly as a knob bulging from the lower third of the kidney. The center of this bulging area was located 5 cm. from the lower pole, and had a basal diameter of 3.5 cm. and a width of 3 cm. It bulged 1.5 cm. above the surface of the kidney. It was continuous with the main tumor mass described above. Other extensions of the tumor were seen as in the illustrations (figs. 9 and 10). There was no grossly visible capsule separating the tumor from the renal parenchyma. In
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FIG. 10. Sagittal section showing irregular lobulation of fat throughout upper two.thirds of kidney.
FIG. lL Low power view showing adult fat cells, marked vascularity of tumor, and absence of capsule between fatty tumor and renal parenchyma.. a Adu] t fat cell; b blood vessels.
FIG. 12.
Low power view showing cellular, vascular connective tissue mixed with fat
FIG. 13. High power view showing a vascular connective tissue, b adult fat cells, and c embryonal fat. 468
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the upper pole the calyces were elongated and the renal papillae flattened to give the "spider-leg" deformity seen in the roentgenogram. Microscopic Examination: Some portions of the tumor consisted entirely of adult fat cells (figs. 11 and 12). Throughout this fatty tumor there were branching blood vessels which were rather thick-walled structures. In some places considerable connective tissue with collagen fibrils accompanied these blood vessels (fig. 13). In the soft, reddish portion, which was separate, the tumor was composed principally of connective tissue and blood vessels so that in places it looked almost like an hemangioma of the cavernous type. However, one could still see fat cells scattered throughout even in this more vascular area. There was no distinct capsule about any of the tumor tissue. The fat cells lay adjacent to the renal parenchyma and stroma. The blood vessels seemed to be coming out along the border into the substance of the tumor. There were no blood vessels invaded by tumor cells. The kidney parenchyma was essentially unchanged, excepting for replacement and impingement by tumor tissue.
Details of symptoms and pathology of cases collected from the literature. 1. Grawitz: No symptoms given. Pathology: A large tumor, weighing together with the kidney 2,200 gm. and measuring 23 by 19 by 12 cm., extended from the hilus to the cortex of the kidney. It was situated inside the renal capsule. Its main constituent was fat. There was a fibrous compression capsule composed of kidney tissue about it. Some parts of the growth gave the appearance of an arterial angioma with much smooth muscle, these areas appearing like myoma, but even here fat lobules were present. 2, Alsberg: Symptoms: Pelvic pain. Large, freely movable tumor, the size of a child's head, was located in the region of the right kidney. Pathology: There were multiple lipomas varying from the size of a millet seed to that of a waL,ut with one small adrenal rest. The tumors were scattered evenly through the organ, both in the cortex and medullary areas. Large nodules sharply delineated from the kidney substance, and could be easily enudeated. Microscopically many of these tumors consisted of pure fat, while in the others there was abundant fibrous tissue. Some areas showed an appearance suggestive of spindle cell sarcoma with overgrowth of vessels. 3. Warthin: Tumor discovered at childbirth, which required instrumental delivery. Pathology: The kidney and tumor weighed 908 gm. and measured 14 by 8 by 6 cm. The tumor extended, cordlike, into the upper end of the ureter for 6 inches in length, with the diameter of
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THOMAS D. ROBERTSON AND JOHN R. HAND
this area 1 inch. This extension was smooth and blunt below. It was unattached to the ureteral wall, and there was complete filling of the lumen. The pelvis was dilated, and completely filled by tumor. There was some mucinous degeneration. The tumor was well differentiated. 4. Bartsch: Symptoms: Increase in size of abdomen for 6 years, pain while walking for 3 weeks, frequency for 2 years, no hematuria. Right
1.01s qm 12
Fm. 14. Schematic drawings, from authors' descriptions, of intrarenal lipomas removed surgically.
abdominal mass. Pathology: The kidney and tumor weighed 2,250 gm. and measured 19 by 12 by 25 cm. The tumor separated the 2 poles of the kidney. It was composed mostly of pure fat. The rest was vascular and fibrous, with smooth muscle around the vessels. There was a capsule present in some places, and in other areas fatty tumor tissue lay directly against the kidney tissue. The calyces were compressed the tumor. 5. Keenan and Archibald: Symptoms: Attacks of dull pain in the right side, lump in the right side. Pathology: The kidney weighed
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350 gm., including the tumor. The tumor itself measured 4.7 cm. in diameter, with the kidney measuring 9.5 by 8.5 by 5.7 cm. The tumor was sharply demarcated from the surrounding kidney tissue, and occupied the center of the convexity. It appeared to divide the kidney poles transversely and longitudinally underneath the capsule. The pelvis was unchanged excepting by the dilatation. The tumor was globular on cut section, with an indefinite capsule. At the center the tumor appeared to consist of ordinary fat without lobulation. This shaded off to a more friable zone of grayish color which showed considerable reddish-brown mottling, giving the impression that it was stained by extravasated blood. Two small fatty looking areas, about 3 cm. in diameter, were present deep in the kidney in the upper pole, separated from the larger tumor. They had no capsule. Microscopically the tumor was mainly thick walled, and surrounded by what appeared on superficial examination to be young fibrous tissue, while here and there, though mainly at the periphery, there were small areas of large, irregularly shaped, fatcontaining cells of indeterminate type. A section of this tumor was not available. There was a question in our minds whether this was really a lipoma, but a detailed discussion seems to leave little doubt that it was . 6. Hinz: Symptoms: Colicky, right upper quadrant pain. On examination the right upper abdomen was found to be rigid, and a diagnosis of chol.ecystitis with stones was made. The gall-bladder on exploration was found to be normal. But a large mass was noted in the region of the right kidney. Cystoscopic examination on the table showed the kidney to be normal. The patient was then turned over, and a right nephrectomy was performed. It was noted that hemorrhage had occurred about the kidney. Pathology: The kidney was 12 cm. long. After stripping the capsule, needlehead to pea sized nodules could be seen irregularly distributed over the surface of the kidney. These were attached to the capsule, but had not broken through. In cross section it was noted that 1 large tumor extended to the kidney pelvis. All the nodules were surrounded by normal kidney tissue. Microscopic diagnosis was myolipoma. 7. Lower and Belcher. Symptoms: Pain, indigestion, nervousness of 11 months' duration, loss of 12 pounds in weight during the month before admission, mass in the left kidney region. Pyelogram showed deformity of the left pelvis strongly suggestive of new growth. Patient was rather emaciated. Pathology: In the middle of the kidney, on the lateral surface, there was an almost globular, subcapsular mass, 4 inches in diame-
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THOMAS D. ROBERTSON AND JOHN R. HAND
ter, fairly well encapsulated, and compressing the pelvis. It weighed 420 gm. The renal vessels were not involved. Microscopically fat and fibrous tissue with no true capsule was noted. 8. Hunt and Simon: Symptoms: For 2 years distress in the right lumbar region, severe for 2 months. Hematuria for 10 days, becoming marked. Urgency, frequency, dysuria, loss of 10 pounds in 1 month, and anemia. Pyelogram showed the lower calyx to be slightly dilated, and the minor calyx to be elongated. Pathology: Tumor 2.5 cm. in diameter on the anterior surface of the kidney. It could not be enucleated at operation. The yellow tumor extended down to the pelvis. It was not encapsulated, but was sharply demarcated. Microscopically it showed adult fat with many vascular channels surrounded by islands of moderately dense fibrous tissue. Fibrous tissue comprised about onethird of the total volume. Occasional myxomatous areas were noted. 9. Nicholson and Gillespie. Symptoms: Severe abdominal pain in the right side and hematuria of 3 days' duration. Blood pressure was 280/140. There was tenderness in the right kidney region. Cystoscopic examination showed blood coming from the right meatus. Pyelograms showed deformity of the right pelvis. A diagnosis was made of intrarenal hemorrhage or malignancy. On exploration a large mass, which was formed by a massive hemorrhagic infiltration, was found in the region of the right kidney. Pathology: The kidney measured 16 by 8.5 by 6.5 cm. A large hematoma was found on the upper pole of the kidney. In the upper half of the kidney there was a yellowish tumor measuring 2.6 by 3.5 by 2.5 cm., involving the medullary and cortical substance of the kidney and completely replacing it. The tumor was definitely demarcated from the kidney substance. Microscopic examination showed sections from various places in the tumor to be composed of adult adipose tissue. Diagnosis was lipoma of the kidney with partial necrosis and extensive subcapsular and intrapelvic hemorrhages. 10. Vertova: Symptoms: Pain in the right lower abdomen for 19 years, constipation, slight fever. Onset was sudden, with pain, hematuria, and albuminuria rapidly progressing to uremia. But this cleared up nicely. The urine was normal. Uroselectan showed normal calyces. The kidney was irregular in shape, and enlarged in the lower portion. Pathology: The kidney weighed 650 gm. It was ovoid, and measured 14 cm. in length, 10 cm. in width, and 6 cm. in thickness. There were many subcapsular nodules of various sizes, with the smallest the size of a grain of rice. At each pole there was a nodule the size of a walnut, and in the posterior part of the kidney there was one the size of an orange.
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The color of these nodules was grayish-yellow. Microscopically the tumor tissue was in direct contact with the kidney tissue, with no true capsule. A connective tissue capsule surrounded the smallest nodule. The tumors consisted mostly of adult fibrous connective tissue. The vessels were numerous in places. Fat appeared especially at the edge at various points. There were no glands, smooth muscle, or cartilage. 11. Pemberton and McCaughan: Syrn.ptoms: Intermittent attacks of diarrhea with generalized abdominal cramps of 12 months' duration. Tumor in the left upper quadrant. Negative intravenous urograms. Pathology: The kidney and tumor weighed 850 gm. and measured 15 by 12 by 12 cm. The tumor was attached to the lower pole of the kidney, necessitating removal of the tip of the lower pole. The kidney capsule was reflected over the tumor which did not extend deeply into the kidney. Microscopically the tumor was shown to be composed mainly of adult adipose tissue with a few embryonal fat cells. There was a scant amount of connective tissue around the blood vessels. The blood vessels to the tumor came from the kidney cortex. 12. Potter :2 Symptoms: Pain and a mass in the right side, indigestion, dizziness, headaches, nervousness, fatigue, and loss of weight. Pathology: The gross specimen was a large kidney and tumor weighing 1.015 gm. and measuring 24 by 19 by 15 cm. In the middle and posterior portions of the lateral surface there was a large, nodular, encapsulated tumor dividing the kidney both ways. The largest part of the specimen consisted of the tumor mass which was fairly well encapsulated. A few blood clots in the tumor showed central necrosis. The tumor itself was of nodular structure, yellowish in color, mottled in appearance, and of medium consistency. In intact areas of the kidney there were secondary nodules up to the size of a plumb. In the parts adjoining the tumor the kidney tissue was separated from the tumor by a small amount of coarse connective tissue which was very rich in hyperemic blood vessels. The blood vessels frequently showed marked hyaline degeneration of their walls which were exceedingly thickened. The ureter was 13 cm. long and intact. The renal pelvis was narrowed. Microscopic sections were characterized by a typical lipomatous structure which included fibrous connective tissue. SUMMARY
Twelve cases of primary intrarenal lipoma, removed surgically, have been collected from the literature. Two additional cases are presented, 2
The cases of Wells and Chevennaz, reported by Potter, could not be confirmed.
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These tumors, because of their cortical and subcortical position in kidney, may attain considerable size before giving rise to symptoms. Pain and hematuria may call attention to the presence of such a tumor at an early date. Clinically primary renal lipoma may be indistinct from primary renal carcinoma. The 2 cases reported herein were thought to be renal carcinoma. Pathologic examination, however, showed them to be benign intrarenal lipomas. This is the most important feature of these case reports, as the prognosis in the 2 conditions is decidedly different. A primary renal carcinoma of the size noted in these 2 cases would, no doubt, terminate fatally. The 2 patients whose cases we report are well today and present no evidence of recurrence. Intrarenal lipomas may contain variable amounts of connective tissue, smooth muscle, myxomatous vascular tissue, and cartilage, or they may show sarcomatous transformation (no true sarcomas of this type been reported to our knowledge). A new concept of the origin of primary intrarenal lipoma is suggested: namely, that these tumors arise from the embryonic connective tissue surrounding the developing collecting tubules. The embryonic connec, tive tissues may be pushed to a cortical or subcapsular position by the developing collecting tubule buds. We wish to express our appreciation to Dr. Herbert Thatcher and Dr, John Cheetham, of Portland, for allowing us to report Case 1. We also wish to thank Dr. Adolph A. Kutzmann, of Los Angeles, for calling our attention to the cases reported by Hinz and Nicholson and Gillespie. REFERENCES ALSBERG, A.: Case report of a lipoma of the kidney. Arch. f. klin. Chlr., 44: 458, 1892. BARTSCH, C.: Ueber einem seltenen Fall von Nierenlipom. Greisswald, 1900. GRA,VITZ, P.: Arch. f. Path. Anat. u. Physiol., 93: 39-63, 1883. HINZ, R.: Massenblutung ins Nierenlager bei Myolipom. Arch. f. klin. Chir., 132: 149-155, 1924. HUNT, VERNE C., AND SnwN, HAROLD E.: Perirenal and intrarenal lipoma. Am. J. Surg., 4: 390--395, 1928. KEENAN, C. B., AND ARCHIBALD, E. W.: Fatty tumor of kidney suggesting a metamorphosis of adrenal cells into true fat. J. Med. Research, 16: 121, 1907. LOWER, W. E., AND BELCHER, G. W.: Massive lipoma of the kidney, Surg., Gynec. and Obst, 45: 1-6, 1927. NICHOLSON, M.A., AND GILLESPIE, M. G.: Lipoma of the kidney, report of a case. J. Urol., 26: 395-403, 1931. PEMBERTON, J. DE J., AND MCCAUGHAN, J. M.: Intrarenal and perirenal lipomata, Surg,, and Obst., 66: 110--115, 1933. POTTER, ALFRED H.: Massive renallipoma, Urol. and Cu tan. Rev., 40: 717-724, 1936. VERT0VA, G.: Su di un caso di tumore benigno rare non ipemefroide del rene destro. Tumori, 6: 620-633, J.932. Abstr. Am. J. Cane., 19: 956 1933. W ARTHIN, A. S.: Fibro-lipoma of the kidney, J. Path. and Bact., 4: 404-411, 1897.