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Adenomatoid Tumors of the Epididymis: Report of Three Cases
ADENOMATOID TUMORS OF THE EPIDIDYMIS: REPORT OF THREE CASES JOHN T. coDNERE, CAPT., M.C., A.u.s.,· AND JOSEPH E. FLYNN, MAJOR, M.c., A.U.S.
From the Army and Navy General Hospital, Hot Springs National Park, Ark.
Golden and Ash1 recently reported 15 cases of benign primary neoplasms of the genital tract under the term adenomatoid tumors. Similar tumors, as pointed out by these authors, have been previously reported in the literature under such designations as mesothelioma, adenocarcinoma grade one, leiomyoma, lymphangioma, and others. Theories concerning the parent tissue of these tumors about equal the number of observers. The first unequivocal adenomatoid tumor was reported by Sakaguchi2 who used the term "adenomyoma." The second report was by Hinman and Gibson 3 in 1924. The tumor reported by Hinman and Gibson was reviewed by several eminent pathologists. The concensus of opinion was that the neoplasm could best be classified as a scirrhous adenocarcinoma of a low degree of malignancy. Ewing's comment, quoted by Hinman and Gibson, was as follows: "Structurally, your tumor of the epididymis is an adenocarcinoma, being composed of widely scattered acini lined by flat or often cubical epithelioid cells in which the nuclei and nucleoli are prominent. Many of the acini are widely dilated and the lining cells flattened so that these portions recall a lymphangioma. The general structure recalls that of the rete testis, but the tumor seems to have been entirely separate from the testis, so that an origin from the rete is not easily adjusted. That it has some malignancy is shown by the infiltration of the skin, but I should not regard it as very malignant. I am quite unable to reach any conclusion regarding the origin of the tumor. Some years ago I saw a very similar growth removed from the cord, and I concluded that it was a lymphangioma, but this conclusion can hardly be regarded as satisfactory. The occurrence of such a tumor suggests to me a search for aberrant canals of embryonal origin in this locality which might give rise to such a tumor. This region abounds in peculiar structures of undetermined nature, which might give rise to tumors. Of aberrant canals from the rete I know nothing. The possibility of an origin from lymph canals is perhaps worth considering, but lacks any definite support." Gordon-Taylor and Omanney-Davis4 believe that these tumors are derived from aberrant cells in connection with the mesonephric ducts that become sequestrated during embryonic life, 1 Golden, A. and Ash, J.E.: Adenomatoid tumors of the genital tract. Am. J. Path., 21: 63-79, 1945. 2 Sakaguchi, Y.: Uber das Adenomyom des Nebenhodens, Frankfurt, Ztschr. f. Path., 18: 379-387, 1915-16. 3 Hinman, F ., and Gibson, T. E.: Tumors of the epididymis, spermatic cord and testicular tunics. A review of the literature and report of three new cases. Arch. Surg., 8: 100-137, 1924. 4 Gordon-Taylor, G., and Ommaney-Davis, C., A case of adenoma of the epididymis, with a note on solid tumours of the epididymis. Brit. J. Surg., 29: 260-262, 1941.
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ADENOMATOID TUMORS OF EPIDIDYMIS
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and, after lying dormant for years, take on active growth. Evans"· 6 believed that these neoplasms are derived from mesothelial cell-; of the serosa of the tunica vaginalis; therefore he used the term mesothelioma. In accordance with the view of Gordon-Taylor and Omanney-Davis, the au.thors favor the mesonephrogenic origin. There can be no doubt concerning the sinlilarity of cytoarchitectonics of adenomatoid tumors to the mesonephros. This pathogenesis is further suggested by the fact that the caput major of the epididymis contains efferent ductules derived from the cranial group of mesonephric tubules, while the caudal group of the mesonephric tubules becomes vestigal and persists as aberrant ductules in the lower portion of the epididymis. The clinical features and pathology of these tumors are illustrated by the following case reports. CASE REPORTS
Case 1. AMM Acc. 141712, a 26-year-old white male, was admitted to the hospital June 22, 1945 with the complaint of a "nodule on the upper part of the left testicle." When first noticed in September 1944, the nodule was described as being painless, hard and the size of a pea. A gradual increase in size, to that of a grape, was observed during the next 10 months. This increase in size was not associated with weight loss. The family and past histories were irrelevant. He denied venereal disease and did not recall ever receiving an injury to the scrotum. The physical examination, except for the genitalia, was essentially negative. The penis and right scrotal contents were normal. Examination of the left scrotal contents revealed a hard, non-tender, ,smooth, spheroidal mass, 2 by 2 cm. in size, occupying the region of the caput major of the epididymis. The testis and lower portion of the spermatic cord were normal. The preoperative diagnosis was neoplasm of epididymis, caput major, left, adenomatoid type. At operation June 28 the caput major of the left epididymis was enlarged to approximately 2 cm. in diameter by a smooth firm spheroidal mass of pinkish color. The remainder of the epididymis appeared normal. An epididymectomy was performed. The neoplasm was separated from the tunica albuginea by sharp dissection. There was no evidence of testicular involvement. The gross specimen (fig. 1) consisted of an epididymis. The entire specimen measured about 8 cm. in length. At the caput major of the epididymis was a circumscribed enlargement that measured 1.8 cm. in width and 1.2 cm. in thickness. This tumor mass extended about 1½ beyond the appendix of the epididymis. The tumor mass was firm, solid and made up of a grayish white tissue. With the larger specimen was a small oval-shaped piece of tissue measuring 1.3 mm. in length and approximately 5 mm. in its greatest width. It was made up of tissue similar to the above tumor. The remainder of the epididymis appeared perfectly normal.
cm.
5 Evans, N., Mesothelioma of the epididymis and tunica vaginalis. J. Urol., 60: 249-254, 1943. 6 Evans, N.: Mesotheliomas of the uterine and tubal serosa and the tunica vaginalis testis. Am. J. Path., 19: 461-471, 1943.
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JOHN T. CODNERE AND JOSEPH E. FLYNN
Microscopic sections of the tumor in the caput major showed a considerable portion of the epididymis to be replaced by dense fibrillar stroma in which were imbedded cells that varied considerably in size, shape and area (fig. 2). Some
Frn. 1. Case 1.
Photograph of epididymis.
Arrow points to tumor of caput major
Frn. 2. Case 1. Photomicrograph of tumor involving caput major. Note numerous spaces imbedded in fibrillar stroma. Spaces are lined by epithelial-like cells. AMM Neg. 90364, X 145.
of the cells manifested a distinct organoid tendency. These cells were cuboidal to flattened and often surrounded a clear space. In a few places these spaces anastomosed to produce labyrinths of various sizes and shapes. In addition to the components that produced an organoid appearance, there were many areas
ADENOMATOID TUMORS OF EPIDIDYMIS
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where the cells were arranged in irregular cords. The cells in such cords ,vere round to polyhedral with abundant vacuolated cytoplasm and irregular nuclei. The nuclei sometimes contained a central nucleolus with the remainder of the chromatin very finely distributed. An occasional cell was encountered in which the cytoplasm contained a large vacuolated inclusion. In some areas the cells that were arranged in cords or acinar-like structures appear to fade almost imperceptibly into the adjacent stroma. The tubules of the epididymis still remaining were relatively normal. Sections of the small piece of tumor submitted with the larger specimen showed essentially the same cytoarchitectonics as described above. Sections from the grossly normal epididymis showed no significant alterations. Diagnosis: Adenomatoid tumor of the epididymis. Case 2. AMM Acc. 119596, a 33-year-old white male, was admitted October 20, 1944 for deep x-ray therapy following the removal of a suspected malignant lesion of the right epididymis on August 4. In 1937 the patient noticed a small nodule in the upper right scrotum. The nodule was not painful. He denied venereal disease. There was no history of injury to the scrotum. In August, 1944, following a routine physical, he was advised to have the tumor removed. The tumor ,vas described as follows: A hard, non-tender, spheroidal mass approximately 2.5 cm. in diameter situated in the region of the caput major of the epididymis, but apparently not involving the testis or spermatic cord in the lower portion. Roentgenological examination of the lungs revealed no abnormalities. The hemoglobin was 15.9 gm. The Kahn test was negative. Preoperative diagnosis: Neoplasm of the epididymis. On August 4 a right epididymectomy was performed. The operator stated that the caput major was 5 times normal size. Pathological report (George T. Rich, Major, M.C., 147th General Hospital): The gross specimen consisted of a partly encapsulated hemispherical tumor measuring 2.5 cm. in diameter and 1 cm. in thickness. At one end there was a small cord-like structure protruding from the capsule. This mass measured 1.2 cm. in length and 0.3 cm. in diameter. On cut section the tumor was grayish white with glistening strands of dense tissue coursing throughout. On microscopic examination the tumor was encapsulated with a thin dense fibrous tissue capsule (fig. 3). .Just beneath the capsule there was an edematous fibrous zone with moderate round cell infiltration and small distended blood vessels. The tumor ·was composed of large cells ,vith indistinct cell boundaries. The cytoplasm took a faint acidophilic stain with fine fibrils coursing longitudinally throughout the cells. The oval nuclei were relatively large ,vith ,vell defined nuclear membranes, prominent chromatin frameworks, and occasional mitotic figures. There ,vere from one to two prominent nucleoli present in each cell. The nucleoli stained acidophilically. A few of the cells had large clear vacuolated areas in their cytoplasm. The cells tended to be arranged in intertwining groups so that they were sectioned longitudinally and on cross section. By l\1asson's technique it was evident that a number of fine fibrous tissue strands coursed throughout the tumor. These cells had fusiform-shaped nuclei with darkly staining chromatin framework. At one corner of the slide there were
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JOHN T. CODNERE AND JOSEPH E. FLYNN
cross sections of tubular structures lined by columnar cells having relatively large nuclei, prominent nucleoli, and conspicuous chromatin framework. A few nests of round cells were seen in this area. The blood vessels were not numerous.
Fm. 3. Case 2. Photomicrograph of cpididymal tumor. Note labyrinth of spaces lined by large vacuolated cells. Surrounding them is a fibrous stroma. A.MM Neg. 90361, X 190.
Fm. 4. Case 3. Photomicrograph of epididymal tumor. Note tubular structures lined by flat to cuboidal epithelial-like cells. Architectural similarity of this tumor to mesonephros is striking. A.MG Neg. 90362, X 130.
Diagnosis: Adenomatoid tumor of the epididymis. In August 1945 there was no evidence of recurrence. Case 3. AMM Acc. 136778, a 47-year-old white male, was admitted to the
ADENOMATOID TUMORS OF EPIDIDYMIS
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hospital May 10, 1945 for treatment of a right inguinal hernia and hydrocele. The hernia had been present since November 16, 1944. The past history and family history were irrelevant. There was no history of scrotal trauma. He denied venereal disease. Physical examination revealed the presence of a reducible inguinal hernia extending into the upper portion of the right side of the scrotum. There were bilateral hydroceles. The hemoglobin was 15 gm. The Kahn test was negative. At operation May 16 a small circumscribed white mass, 1 by 1 cm., was found occupying the region of the caput minor of the right epididymis. 'l7 his was removed in toto and submitted for histopathological examination. The gross specimen consisted of a small, firm circumscribed grayish white mass of tissue measuring 8 by 6 by 5 mm. Microscopic sections of the tumor showed it to consist of a fibrillar stroma in which were imbedded numerous oval to round spaces lined by cells that exhibited a moderate polymorphism (figs. 3 and 4). Many of the spaces ,vere lined by flattened cells the cytoplaem of which appeared to form a more or less continuous plate. The nuclei of these cells were either hyperchromatic or vesicular. Other spaces were lined by cul:oidal cells having vague outlines and pyknotic nuclei. Still other spaces were lined by cells with protoplasmic prolongations that bridged the spaces, subdividing them into multilocular compartments. These cytoplasmic prolongations were pale-staining and refractile. The pathogenesis of these cellular-lined spaces could be seen by the presence of small islands made up of polyhedral to triangular-shaped cells in which were oval nuclei that usually contained a small centrally located nucleolus. Every gradation from such a solid island to the large multilocular space ,vas present. The fibrillar stroma varied considerably. In some places it was quite cellular, containing nuclei that in profile were cylindrical with delicately rounded ends. In other areas the stroma contained only a few cells. At the margins there were focal infiltrates of lymphocytes. Diagnosis: Adenomatoid tumor, epididymis. SUMMARY
Three cases of adenomatoid tumors of the epididymis are reported. Adenomatoid tumors of the epididymis are globular or oval in shape, less than 2 to 3 cm. in diameter, sharply circumscribed, and encapsulated. The cut surface is firm and white to gray. Microscopically, these tumors consist of a fibrillar stroma in which are imbedded tubular-like structures lined by cuboidal to flattened cells having prominent dark staining or vesicular nuclei and acidophilic cytoplasm. On the basis of histological similarity, aberrant mesonephrogenic structures are thought to constitute the genetic foundation of these neoplasms. This is in accordance with the pathogenesis suggested by Gordon-Taylor and OmanneyDavis.
From the Army and Navy General Hospital, Hot Springs National Park, Ark.
Golden and Ash1 recently reported 15 cases of benign primary neoplasms of the genital tract under the term adenomatoid tumors. Similar tumors, as pointed out by these authors, have been previously reported in the literature under such designations as mesothelioma, adenocarcinoma grade one, leiomyoma, lymphangioma, and others. Theories concerning the parent tissue of these tumors about equal the number of observers. The first unequivocal adenomatoid tumor was reported by Sakaguchi2 who used the term "adenomyoma." The second report was by Hinman and Gibson 3 in 1924. The tumor reported by Hinman and Gibson was reviewed by several eminent pathologists. The concensus of opinion was that the neoplasm could best be classified as a scirrhous adenocarcinoma of a low degree of malignancy. Ewing's comment, quoted by Hinman and Gibson, was as follows: "Structurally, your tumor of the epididymis is an adenocarcinoma, being composed of widely scattered acini lined by flat or often cubical epithelioid cells in which the nuclei and nucleoli are prominent. Many of the acini are widely dilated and the lining cells flattened so that these portions recall a lymphangioma. The general structure recalls that of the rete testis, but the tumor seems to have been entirely separate from the testis, so that an origin from the rete is not easily adjusted. That it has some malignancy is shown by the infiltration of the skin, but I should not regard it as very malignant. I am quite unable to reach any conclusion regarding the origin of the tumor. Some years ago I saw a very similar growth removed from the cord, and I concluded that it was a lymphangioma, but this conclusion can hardly be regarded as satisfactory. The occurrence of such a tumor suggests to me a search for aberrant canals of embryonal origin in this locality which might give rise to such a tumor. This region abounds in peculiar structures of undetermined nature, which might give rise to tumors. Of aberrant canals from the rete I know nothing. The possibility of an origin from lymph canals is perhaps worth considering, but lacks any definite support." Gordon-Taylor and Omanney-Davis4 believe that these tumors are derived from aberrant cells in connection with the mesonephric ducts that become sequestrated during embryonic life, 1 Golden, A. and Ash, J.E.: Adenomatoid tumors of the genital tract. Am. J. Path., 21: 63-79, 1945. 2 Sakaguchi, Y.: Uber das Adenomyom des Nebenhodens, Frankfurt, Ztschr. f. Path., 18: 379-387, 1915-16. 3 Hinman, F ., and Gibson, T. E.: Tumors of the epididymis, spermatic cord and testicular tunics. A review of the literature and report of three new cases. Arch. Surg., 8: 100-137, 1924. 4 Gordon-Taylor, G., and Ommaney-Davis, C., A case of adenoma of the epididymis, with a note on solid tumours of the epididymis. Brit. J. Surg., 29: 260-262, 1941.
448
ADENOMATOID TUMORS OF EPIDIDYMIS
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and, after lying dormant for years, take on active growth. Evans"· 6 believed that these neoplasms are derived from mesothelial cell-; of the serosa of the tunica vaginalis; therefore he used the term mesothelioma. In accordance with the view of Gordon-Taylor and Omanney-Davis, the au.thors favor the mesonephrogenic origin. There can be no doubt concerning the sinlilarity of cytoarchitectonics of adenomatoid tumors to the mesonephros. This pathogenesis is further suggested by the fact that the caput major of the epididymis contains efferent ductules derived from the cranial group of mesonephric tubules, while the caudal group of the mesonephric tubules becomes vestigal and persists as aberrant ductules in the lower portion of the epididymis. The clinical features and pathology of these tumors are illustrated by the following case reports. CASE REPORTS
Case 1. AMM Acc. 141712, a 26-year-old white male, was admitted to the hospital June 22, 1945 with the complaint of a "nodule on the upper part of the left testicle." When first noticed in September 1944, the nodule was described as being painless, hard and the size of a pea. A gradual increase in size, to that of a grape, was observed during the next 10 months. This increase in size was not associated with weight loss. The family and past histories were irrelevant. He denied venereal disease and did not recall ever receiving an injury to the scrotum. The physical examination, except for the genitalia, was essentially negative. The penis and right scrotal contents were normal. Examination of the left scrotal contents revealed a hard, non-tender, ,smooth, spheroidal mass, 2 by 2 cm. in size, occupying the region of the caput major of the epididymis. The testis and lower portion of the spermatic cord were normal. The preoperative diagnosis was neoplasm of epididymis, caput major, left, adenomatoid type. At operation June 28 the caput major of the left epididymis was enlarged to approximately 2 cm. in diameter by a smooth firm spheroidal mass of pinkish color. The remainder of the epididymis appeared normal. An epididymectomy was performed. The neoplasm was separated from the tunica albuginea by sharp dissection. There was no evidence of testicular involvement. The gross specimen (fig. 1) consisted of an epididymis. The entire specimen measured about 8 cm. in length. At the caput major of the epididymis was a circumscribed enlargement that measured 1.8 cm. in width and 1.2 cm. in thickness. This tumor mass extended about 1½ beyond the appendix of the epididymis. The tumor mass was firm, solid and made up of a grayish white tissue. With the larger specimen was a small oval-shaped piece of tissue measuring 1.3 mm. in length and approximately 5 mm. in its greatest width. It was made up of tissue similar to the above tumor. The remainder of the epididymis appeared perfectly normal.
cm.
5 Evans, N., Mesothelioma of the epididymis and tunica vaginalis. J. Urol., 60: 249-254, 1943. 6 Evans, N.: Mesotheliomas of the uterine and tubal serosa and the tunica vaginalis testis. Am. J. Path., 19: 461-471, 1943.
450
JOHN T. CODNERE AND JOSEPH E. FLYNN
Microscopic sections of the tumor in the caput major showed a considerable portion of the epididymis to be replaced by dense fibrillar stroma in which were imbedded cells that varied considerably in size, shape and area (fig. 2). Some
Frn. 1. Case 1.
Photograph of epididymis.
Arrow points to tumor of caput major
Frn. 2. Case 1. Photomicrograph of tumor involving caput major. Note numerous spaces imbedded in fibrillar stroma. Spaces are lined by epithelial-like cells. AMM Neg. 90364, X 145.
of the cells manifested a distinct organoid tendency. These cells were cuboidal to flattened and often surrounded a clear space. In a few places these spaces anastomosed to produce labyrinths of various sizes and shapes. In addition to the components that produced an organoid appearance, there were many areas
ADENOMATOID TUMORS OF EPIDIDYMIS
451
where the cells were arranged in irregular cords. The cells in such cords ,vere round to polyhedral with abundant vacuolated cytoplasm and irregular nuclei. The nuclei sometimes contained a central nucleolus with the remainder of the chromatin very finely distributed. An occasional cell was encountered in which the cytoplasm contained a large vacuolated inclusion. In some areas the cells that were arranged in cords or acinar-like structures appear to fade almost imperceptibly into the adjacent stroma. The tubules of the epididymis still remaining were relatively normal. Sections of the small piece of tumor submitted with the larger specimen showed essentially the same cytoarchitectonics as described above. Sections from the grossly normal epididymis showed no significant alterations. Diagnosis: Adenomatoid tumor of the epididymis. Case 2. AMM Acc. 119596, a 33-year-old white male, was admitted October 20, 1944 for deep x-ray therapy following the removal of a suspected malignant lesion of the right epididymis on August 4. In 1937 the patient noticed a small nodule in the upper right scrotum. The nodule was not painful. He denied venereal disease. There was no history of injury to the scrotum. In August, 1944, following a routine physical, he was advised to have the tumor removed. The tumor ,vas described as follows: A hard, non-tender, spheroidal mass approximately 2.5 cm. in diameter situated in the region of the caput major of the epididymis, but apparently not involving the testis or spermatic cord in the lower portion. Roentgenological examination of the lungs revealed no abnormalities. The hemoglobin was 15.9 gm. The Kahn test was negative. Preoperative diagnosis: Neoplasm of the epididymis. On August 4 a right epididymectomy was performed. The operator stated that the caput major was 5 times normal size. Pathological report (George T. Rich, Major, M.C., 147th General Hospital): The gross specimen consisted of a partly encapsulated hemispherical tumor measuring 2.5 cm. in diameter and 1 cm. in thickness. At one end there was a small cord-like structure protruding from the capsule. This mass measured 1.2 cm. in length and 0.3 cm. in diameter. On cut section the tumor was grayish white with glistening strands of dense tissue coursing throughout. On microscopic examination the tumor was encapsulated with a thin dense fibrous tissue capsule (fig. 3). .Just beneath the capsule there was an edematous fibrous zone with moderate round cell infiltration and small distended blood vessels. The tumor ·was composed of large cells ,vith indistinct cell boundaries. The cytoplasm took a faint acidophilic stain with fine fibrils coursing longitudinally throughout the cells. The oval nuclei were relatively large ,vith ,vell defined nuclear membranes, prominent chromatin frameworks, and occasional mitotic figures. There ,vere from one to two prominent nucleoli present in each cell. The nucleoli stained acidophilically. A few of the cells had large clear vacuolated areas in their cytoplasm. The cells tended to be arranged in intertwining groups so that they were sectioned longitudinally and on cross section. By l\1asson's technique it was evident that a number of fine fibrous tissue strands coursed throughout the tumor. These cells had fusiform-shaped nuclei with darkly staining chromatin framework. At one corner of the slide there were
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JOHN T. CODNERE AND JOSEPH E. FLYNN
cross sections of tubular structures lined by columnar cells having relatively large nuclei, prominent nucleoli, and conspicuous chromatin framework. A few nests of round cells were seen in this area. The blood vessels were not numerous.
Fm. 3. Case 2. Photomicrograph of cpididymal tumor. Note labyrinth of spaces lined by large vacuolated cells. Surrounding them is a fibrous stroma. A.MM Neg. 90361, X 190.
Fm. 4. Case 3. Photomicrograph of epididymal tumor. Note tubular structures lined by flat to cuboidal epithelial-like cells. Architectural similarity of this tumor to mesonephros is striking. A.MG Neg. 90362, X 130.
Diagnosis: Adenomatoid tumor of the epididymis. In August 1945 there was no evidence of recurrence. Case 3. AMM Acc. 136778, a 47-year-old white male, was admitted to the
ADENOMATOID TUMORS OF EPIDIDYMIS
453
hospital May 10, 1945 for treatment of a right inguinal hernia and hydrocele. The hernia had been present since November 16, 1944. The past history and family history were irrelevant. There was no history of scrotal trauma. He denied venereal disease. Physical examination revealed the presence of a reducible inguinal hernia extending into the upper portion of the right side of the scrotum. There were bilateral hydroceles. The hemoglobin was 15 gm. The Kahn test was negative. At operation May 16 a small circumscribed white mass, 1 by 1 cm., was found occupying the region of the caput minor of the right epididymis. 'l7 his was removed in toto and submitted for histopathological examination. The gross specimen consisted of a small, firm circumscribed grayish white mass of tissue measuring 8 by 6 by 5 mm. Microscopic sections of the tumor showed it to consist of a fibrillar stroma in which were imbedded numerous oval to round spaces lined by cells that exhibited a moderate polymorphism (figs. 3 and 4). Many of the spaces ,vere lined by flattened cells the cytoplaem of which appeared to form a more or less continuous plate. The nuclei of these cells were either hyperchromatic or vesicular. Other spaces were lined by cul:oidal cells having vague outlines and pyknotic nuclei. Still other spaces were lined by cells with protoplasmic prolongations that bridged the spaces, subdividing them into multilocular compartments. These cytoplasmic prolongations were pale-staining and refractile. The pathogenesis of these cellular-lined spaces could be seen by the presence of small islands made up of polyhedral to triangular-shaped cells in which were oval nuclei that usually contained a small centrally located nucleolus. Every gradation from such a solid island to the large multilocular space ,vas present. The fibrillar stroma varied considerably. In some places it was quite cellular, containing nuclei that in profile were cylindrical with delicately rounded ends. In other areas the stroma contained only a few cells. At the margins there were focal infiltrates of lymphocytes. Diagnosis: Adenomatoid tumor, epididymis. SUMMARY
Three cases of adenomatoid tumors of the epididymis are reported. Adenomatoid tumors of the epididymis are globular or oval in shape, less than 2 to 3 cm. in diameter, sharply circumscribed, and encapsulated. The cut surface is firm and white to gray. Microscopically, these tumors consist of a fibrillar stroma in which are imbedded tubular-like structures lined by cuboidal to flattened cells having prominent dark staining or vesicular nuclei and acidophilic cytoplasm. On the basis of histological similarity, aberrant mesonephrogenic structures are thought to constitute the genetic foundation of these neoplasms. This is in accordance with the pathogenesis suggested by Gordon-Taylor and OmanneyDavis.