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Benign Mixed Epithelial and Stromal Tumor of the Kidney
PATHOLOGY RESEARCH AND PRACTICE
© Gustav Fischer Verlag
Benign Mixed Epithelial and Stromal Tumor of the Kidney Michal Michal 1 and Martin Syrucek 2 ,Department of Pathology, Medical Faculty, Charles University, Pilsen, Czech Republic; 2Department of Pathology, Hospital Na Homolce, Prague, Czech Republic
Summary
We describe a distinctive benign tumor of the kidney in a 48-year-old woman, which was composed of well differentiated ducts set in the spindle cell stroma which was muscle actin, smooth muscle actin and desmin positive, and was morphologically similar to the ovarian stroma. No immature appearing epithelial renal or mesenchymal tissue was present in the tumor. Histologically, the tumor differed from the nephrogenic adenofibroma and the rare cases of adult Wilms tumors, mesoblastic nephromas and cystic nephromas. Key words: Kidney - Benign mixed epithelial and stromal tumor of the kidney - Adenoma with ovarian-like stroma - Cystic nephroma - Nephrogenic adenofibroma
Introduction
Most of the common epithelial renal cell neoplasms arising in adults can be classified as one of the types of carcinoma (clear cell, papillary, granular cell, chromophobe cell, sarcomatoid and collecting duct types), renal cortical adenoma or oncocytoma [7]. Beside these relatively common epithelial tumors, there is a group of renal epithelial tumors or renal tumors with both epithelial and mesenchymal differentiation, which can rarely arise in the adult kidney such as renal carcinoid, small cell carcinoma or adult nephroblastoma, cystic nephroma and mesoblastic nephroma [7]. We describe here a tumor of the kidney arising in an adult woman, which contained both adenomatous epithelial and spindle cell stromal components. The mesenchymal stromal component closely surrounded the epithelial neoplastic tissue. We called the tumor dePathol. Res. Pract. 194: 445-448 (1998)
scriptively benign mixed epithelial and stromal tumor of the kidney (BMEST). To the best of our knowledge, we are unaware of any similar reports in the literature. Case report
A 48-year-old woman who complained of an abdominal mass had excised right kidney with a tumor. The kidney was l6xl4xl2 em. The tumor was localized in the central part of the kidney. It was 10 em in diameter, roundshaped, and well circumscribed with a thin fibrous capsule. There were no signs of infiltrative growth into the surrounding renal parenchyma. The tumor was situated in the renal parenchyma and compressed the adjacent calyceal system. Grossly the tumor had a solid appearance without cyst formation, white color, soft to elastic consistency without hemorrhage and necrosis. Histologically the tumor had adenomatous and distinct mesenchymal components. The adenomatous component was composed of variously large ducts which ranged from very minute, hardly luminized ductuli with a thick basal membrane to larger ducts with well formed lumina (Fig. lA). The largest ducts contained cells with a "hobnail" appearance (Fig. lB). The cytoplasm of the cells of the ducts stained deeply red with eosin stain. The ducts contained PAS and Alcian Blue positive and mucicarmine negative secretion, and the cytoplasm of the cells of the adenomatous component was often deeply eosinophilic. The adenomatous component was accompanied by a characteristic mesAddress for correspondence: Michal Michal, M.D., Department of Pathol. Anatomy; Medical Faculty, Charles University, dr. E. Benese 13, CZ - 305 99 Pilsen, Czech Republic. Fax: ++420-019-273040, Tel.: ++420-019-272896. E-mail: [email protected] 0344-0338/98/0194-0445$5.00/0
446 . M. Michal and M. Syrucek
Fig. 1. Most of the adenomatous component of BMEST was composed of very minute, hardly luminized ductuli with a thick basal membrane (lA, top). The largest ducts contained cells with "hobnail" appearance (1B).
Fig. 2 (top). The mesenchymal component of BMEST was composed of well differentiated spindle cells and which closely resembled ovarian stroma. Fig. 3. The ovarian-like stroma surrounded clusters of small neoplastic ductules or it grew among the larger ducts.
enchymal stroma. It was composed of well differentiated spindle cells which closely resembled ovarian stroma (Fig. 2). Sparse small lymphocytes were spread in the stroma. This ovarian-like stroma surrounded clusters of small neoplastic ductules or grew among the larger ducts (Fig. 3). The stroma was always centered on the adenomatous component and the stroma never formed compact sheets devoid of adenomatous differentiation (Fig. 4). In spite of the similarity of the mesenchymal component of the tumor to ovarian stroma, follicle-like structures, specialized gonadal stromal structures or luteinization characteristic of the ovary were absent in BMEST. No immature embryonal renal tissue, papillary epithelial differentiation, transitional urothelial epithelium or stromal heterologous cellular structures were present in the tumor. No mitoses, atyp-
ias, hemorrhage, necrosis or foci of extramedullary hematopoiesis were observed in BMEST. A pararenal lymph node, which was excised together with the right kidney had a normal structure and was without any tumor. The epithelial tissue reacted with antibodies to cytokeratins AEI-AE3 (monoclonal: Boehringer) and CAM 5.2 (monoclonal: Becton-Dickinson) and it was negative with antibodies to synaptophysin (polyclonal: DAKO), serotonin (polyclonal: DAKO) and chromogranin (monoclonal: DAKO). The eosinophilic cells of the ducts stained strongly with antibody to mitochondrial antigen 113-1 (monoclonal: Biogenex). Antibodies to EMA (monoclonal: DAKO) and carcinoembryonic antigen (polyclonal: DAKO) were only positive in the secret and the superficial glycocalix of the ducts. The cytoplasm of the neoplastic cells was negative. The
Mixed Tumor of the Kidney . 447
Fig. 4. The stroma of BMEST was always centered on the adenomatous component and it never formed compact sheets devoid of adenomatous differentiation.
stroma was negative with all of the above listed antibodies. It was, however, often positive with antibodies to muscle actin HHF 35 (monoclonal: OAKO), smooth muscle actin lA4 (monoclonal: OAKO) and desmin 033 (monoclonal: OAKO). Antibody to the mitochondrial antigen 113-1 stained the stroma weakly. Antibody MIB 1 (monoclonal: Immunotech) only reacted in less then 1% of the epithelial and stromal cells, thus revealing a very low level of the cell proliferation in the tumor.
Discussion It is well known that there are organs beside the ovary, which can give rise to tumors containing ovarian-like stroma in addition to the epithelial component. The best known are cystadenomas and cystadenocarcinomas of the pancreas, liver and biliary system. It is interesting that in addition to containing ovarian-like stroma, these tumors arise exclusively in women [1, 3,4]. In contrast to the cystadenomatous tumors with ovarian-like stroma of the pancreas, liver and the biliary system, the adenomatous component in our case did not have the cystadenomatous arrangement, but was composed of variously large ducts. The "hobnail" appearance of the ductal cells of some of the larger ducts suggests a collecting duct origin of this tumor (Fig. 1B). The strong staining of the ductal epithelial cells with the antibody to the mitochondrial antigen 113-1 proves that the eosinophilia of the epithelial cells in this tumor is caused by high content of mitochondria in the cytoplasm of the tumor cells. However, the granular appearance of the cytoplasm seen in the oncocytomas of the
kidney was lacking. The ovarian-like stroma in our case surrounded clusters of small neoplastic ductules or grew among the larger ducts. It was always centered on the adenomatous component and the stroma never formed compact sheets devoid of adenomatous differentiation (Figs. 3, 4). This morphological feature demonstrates that the ovarian-like stroma in our case is devoid of the capacity for autonomous growth and its development is closely associated with the adenomatous component of the tumor. The actin and desmin positivity in the ovarian-like stroma can be seen in the cystadenomas and cystadenocarcinomas of the liver and the biliary system [4J, as well as in the normal and neoplastic ovarian tumors [8]. The encapsulation of the tumor, the lack of infiltrative growth, mitoses and atypias and the very low rate of proliferation as measured by the staining of the MIB 1 antibody (less than 1%) indicates the benign nature of the tumor. In the differential diagnosis BMEST should be distinguished from several tumors occurring typically in childhood, but rarely arising in adults. The benign morphological features and the lack of the embryonal blastemal tissue differentiates the adenoma of the kidney with the ovarian-like stroma from the rare cases of the adult nephroblastoma [7]. The similarity of the stroma to the ovary well developed encapsulation, lack of widespread myoid stromal differentiation and the absence of foci of extramedullary hematopoiesis distinguish this tumor from the rare examples of mesoblastic nephroma in adults [2, 5J. Most important is the distinction between our case and the nephrogenic adenoma. Nephrogenic adenoma is a recently described tumor arising in the kidney in young people [6]. Histologically it is characterized by a marked predominance of benign-appearing spindled cells encasing nodules of embryonal-appearing epithelium. The epithelial component in nephrogenic adenoma consists of multifocal nests of immature epithelium similar to the hyperplastic nephrogenic rests (nephroblastomatosis) associated with Wilms tumor. Two of the five nephrogenic adenomas contained associated low-grade papillary adenocarcinomas. BMEST lacks any immature renal epithelial tissue or low-grade papillary carcinoma. Moreover, the stroma of the nephrogenic adenoma lacks any actin or desmin positivity, a feature present in the ovarian-like stroma of our case. The finding of the dilated ducts with hobnailed epithelium set in the spindle cell stroma (Fig. lB) raises the possibility of a relationship of our case with cystic nephroma. In comparison with cystic nephroma, however, we did not find in our case any immature embryonal renal tissue, heterologous stromal structures and most importantly, no cystic appearance. It cannot be excluded, however, that our case represents a solid variant of "cystic" nephroma, an entity not yet recognized in any classification. The location in the renal parenchyma and absence of the transitional
448 . M. Michal and M. Syrucek urothelial epithelium clearly distinguishes the BMEST from the recently described cystic hamartoma of the renal pelvis [9]. The lack of mitoses and atypias as well as the low level of proliferation as revealed by MIB I antibody distinguishes the BMEST from the sarcomatoid carcinoma of the kidney.
Acknowledgement: I am most grateful to Dr. Mukensnabl for preparing the figures for this publication, and to the Plzen laboratory staff for their expertise, in particular Mrs. Jana Adamcova. Mrs. Vaclava Winterova is also kindly acknowledged for assistance in typing the manuscript.
2. 3.
4.
5.
Editorial Adendum: The editors would like to note that one of the referees found the tumor presented here to show a considerable similarity to a condition outlined as a "solitary multilocular cyst of the kidney" (segmental cystic disease with the synonyms multilocular cystic nephroma, polycystic nephroma, differentiated nephroblastoma, lymphangioma and papillary cystadenoma) by Bennington and Beckwith [1]. 1. Bennington JL, Beckwith JB (975) Atlas of Tumor Pathology; Tumors of the Kidney, Renal Pelvis, and Ureter. Second Series, Fascicle 12, Repritned 1983, pp 84-85. Armed Forces Institute of Pathology, Washington, D.C.
6. 7.
8.
9.
the pancreas. Morphologic and immunohistochemical observations. Am J Surg Pathol11: 11-20 Block NL, Grabstad HG, Melamed MR (1973) Congenital mesoblastic nephroma (leiomyomatous hamartoma): First adult case. J Urol110: 380-383 Compagno J, Oertel JE (978) Mucinous cystic neoplasms of the pancreas with overt and latent malignancy (cystadenocarcinoma and cystadenoma). A clinicopathologic study of 41 cases. Am J Clin Pathol69: 573-588 Devaney K, Goodman ZD, Ishak KG (994) Hepatobiliary cystadenoma and cystadenocarcinoma. A light microscopic and immunohistochemical study of 70 patients. Am J Surg Pathol18: 1078-2091 Durham JR, Bostwick DG, Farrow GM, Ohorodnik JM (1993) Mesoblastic nephroma of adulthood. Report of three cases. Am J Surg Pathol 17: 1029-1038 Hennigar RA, Beckwith BJ (992) Nephrogenic adenofibroma. A novel kidney tumor of young people. Am J Surg Pathol16: 325-334 Murphy MW, Beckwith JB, Farrow GM (994) Tumors of the kidney, bladder and related urinary structures. Atlas of tumor pathology, fascicle 11, third series. Armed Forces Institute of Pathology, Washington, D.C. Lastaria D, Sachdev RK, Babury RA, YU HM, Nuovo GJ (990) Immunohitochemical analysis for desmin in normal and neoplastic ovarian stromal tissue. Arch Pathol Lab Med 114: 502-505 Pawade J, Soosay GN, Delprado W, Parkinson MC, Rode J (1993) Cystic hamartoma of the renal pelvis. Am J Surg Pathol17: 1169-1175
References I. Albores-Saavedra J, Angeles-Angeles A, Nadji M, Henson DE, Alvarez L (987) Mucinous cystadenocarcinoma of
Received: September 23, 1996 Accepted in revised form: April 16, 1997
© Gustav Fischer Verlag
Benign Mixed Epithelial and Stromal Tumor of the Kidney Michal Michal 1 and Martin Syrucek 2 ,Department of Pathology, Medical Faculty, Charles University, Pilsen, Czech Republic; 2Department of Pathology, Hospital Na Homolce, Prague, Czech Republic
Summary
We describe a distinctive benign tumor of the kidney in a 48-year-old woman, which was composed of well differentiated ducts set in the spindle cell stroma which was muscle actin, smooth muscle actin and desmin positive, and was morphologically similar to the ovarian stroma. No immature appearing epithelial renal or mesenchymal tissue was present in the tumor. Histologically, the tumor differed from the nephrogenic adenofibroma and the rare cases of adult Wilms tumors, mesoblastic nephromas and cystic nephromas. Key words: Kidney - Benign mixed epithelial and stromal tumor of the kidney - Adenoma with ovarian-like stroma - Cystic nephroma - Nephrogenic adenofibroma
Introduction
Most of the common epithelial renal cell neoplasms arising in adults can be classified as one of the types of carcinoma (clear cell, papillary, granular cell, chromophobe cell, sarcomatoid and collecting duct types), renal cortical adenoma or oncocytoma [7]. Beside these relatively common epithelial tumors, there is a group of renal epithelial tumors or renal tumors with both epithelial and mesenchymal differentiation, which can rarely arise in the adult kidney such as renal carcinoid, small cell carcinoma or adult nephroblastoma, cystic nephroma and mesoblastic nephroma [7]. We describe here a tumor of the kidney arising in an adult woman, which contained both adenomatous epithelial and spindle cell stromal components. The mesenchymal stromal component closely surrounded the epithelial neoplastic tissue. We called the tumor dePathol. Res. Pract. 194: 445-448 (1998)
scriptively benign mixed epithelial and stromal tumor of the kidney (BMEST). To the best of our knowledge, we are unaware of any similar reports in the literature. Case report
A 48-year-old woman who complained of an abdominal mass had excised right kidney with a tumor. The kidney was l6xl4xl2 em. The tumor was localized in the central part of the kidney. It was 10 em in diameter, roundshaped, and well circumscribed with a thin fibrous capsule. There were no signs of infiltrative growth into the surrounding renal parenchyma. The tumor was situated in the renal parenchyma and compressed the adjacent calyceal system. Grossly the tumor had a solid appearance without cyst formation, white color, soft to elastic consistency without hemorrhage and necrosis. Histologically the tumor had adenomatous and distinct mesenchymal components. The adenomatous component was composed of variously large ducts which ranged from very minute, hardly luminized ductuli with a thick basal membrane to larger ducts with well formed lumina (Fig. lA). The largest ducts contained cells with a "hobnail" appearance (Fig. lB). The cytoplasm of the cells of the ducts stained deeply red with eosin stain. The ducts contained PAS and Alcian Blue positive and mucicarmine negative secretion, and the cytoplasm of the cells of the adenomatous component was often deeply eosinophilic. The adenomatous component was accompanied by a characteristic mesAddress for correspondence: Michal Michal, M.D., Department of Pathol. Anatomy; Medical Faculty, Charles University, dr. E. Benese 13, CZ - 305 99 Pilsen, Czech Republic. Fax: ++420-019-273040, Tel.: ++420-019-272896. E-mail: [email protected] 0344-0338/98/0194-0445$5.00/0
446 . M. Michal and M. Syrucek
Fig. 1. Most of the adenomatous component of BMEST was composed of very minute, hardly luminized ductuli with a thick basal membrane (lA, top). The largest ducts contained cells with "hobnail" appearance (1B).
Fig. 2 (top). The mesenchymal component of BMEST was composed of well differentiated spindle cells and which closely resembled ovarian stroma. Fig. 3. The ovarian-like stroma surrounded clusters of small neoplastic ductules or it grew among the larger ducts.
enchymal stroma. It was composed of well differentiated spindle cells which closely resembled ovarian stroma (Fig. 2). Sparse small lymphocytes were spread in the stroma. This ovarian-like stroma surrounded clusters of small neoplastic ductules or grew among the larger ducts (Fig. 3). The stroma was always centered on the adenomatous component and the stroma never formed compact sheets devoid of adenomatous differentiation (Fig. 4). In spite of the similarity of the mesenchymal component of the tumor to ovarian stroma, follicle-like structures, specialized gonadal stromal structures or luteinization characteristic of the ovary were absent in BMEST. No immature embryonal renal tissue, papillary epithelial differentiation, transitional urothelial epithelium or stromal heterologous cellular structures were present in the tumor. No mitoses, atyp-
ias, hemorrhage, necrosis or foci of extramedullary hematopoiesis were observed in BMEST. A pararenal lymph node, which was excised together with the right kidney had a normal structure and was without any tumor. The epithelial tissue reacted with antibodies to cytokeratins AEI-AE3 (monoclonal: Boehringer) and CAM 5.2 (monoclonal: Becton-Dickinson) and it was negative with antibodies to synaptophysin (polyclonal: DAKO), serotonin (polyclonal: DAKO) and chromogranin (monoclonal: DAKO). The eosinophilic cells of the ducts stained strongly with antibody to mitochondrial antigen 113-1 (monoclonal: Biogenex). Antibodies to EMA (monoclonal: DAKO) and carcinoembryonic antigen (polyclonal: DAKO) were only positive in the secret and the superficial glycocalix of the ducts. The cytoplasm of the neoplastic cells was negative. The
Mixed Tumor of the Kidney . 447
Fig. 4. The stroma of BMEST was always centered on the adenomatous component and it never formed compact sheets devoid of adenomatous differentiation.
stroma was negative with all of the above listed antibodies. It was, however, often positive with antibodies to muscle actin HHF 35 (monoclonal: OAKO), smooth muscle actin lA4 (monoclonal: OAKO) and desmin 033 (monoclonal: OAKO). Antibody to the mitochondrial antigen 113-1 stained the stroma weakly. Antibody MIB 1 (monoclonal: Immunotech) only reacted in less then 1% of the epithelial and stromal cells, thus revealing a very low level of the cell proliferation in the tumor.
Discussion It is well known that there are organs beside the ovary, which can give rise to tumors containing ovarian-like stroma in addition to the epithelial component. The best known are cystadenomas and cystadenocarcinomas of the pancreas, liver and biliary system. It is interesting that in addition to containing ovarian-like stroma, these tumors arise exclusively in women [1, 3,4]. In contrast to the cystadenomatous tumors with ovarian-like stroma of the pancreas, liver and the biliary system, the adenomatous component in our case did not have the cystadenomatous arrangement, but was composed of variously large ducts. The "hobnail" appearance of the ductal cells of some of the larger ducts suggests a collecting duct origin of this tumor (Fig. 1B). The strong staining of the ductal epithelial cells with the antibody to the mitochondrial antigen 113-1 proves that the eosinophilia of the epithelial cells in this tumor is caused by high content of mitochondria in the cytoplasm of the tumor cells. However, the granular appearance of the cytoplasm seen in the oncocytomas of the
kidney was lacking. The ovarian-like stroma in our case surrounded clusters of small neoplastic ductules or grew among the larger ducts. It was always centered on the adenomatous component and the stroma never formed compact sheets devoid of adenomatous differentiation (Figs. 3, 4). This morphological feature demonstrates that the ovarian-like stroma in our case is devoid of the capacity for autonomous growth and its development is closely associated with the adenomatous component of the tumor. The actin and desmin positivity in the ovarian-like stroma can be seen in the cystadenomas and cystadenocarcinomas of the liver and the biliary system [4J, as well as in the normal and neoplastic ovarian tumors [8]. The encapsulation of the tumor, the lack of infiltrative growth, mitoses and atypias and the very low rate of proliferation as measured by the staining of the MIB 1 antibody (less than 1%) indicates the benign nature of the tumor. In the differential diagnosis BMEST should be distinguished from several tumors occurring typically in childhood, but rarely arising in adults. The benign morphological features and the lack of the embryonal blastemal tissue differentiates the adenoma of the kidney with the ovarian-like stroma from the rare cases of the adult nephroblastoma [7]. The similarity of the stroma to the ovary well developed encapsulation, lack of widespread myoid stromal differentiation and the absence of foci of extramedullary hematopoiesis distinguish this tumor from the rare examples of mesoblastic nephroma in adults [2, 5J. Most important is the distinction between our case and the nephrogenic adenoma. Nephrogenic adenoma is a recently described tumor arising in the kidney in young people [6]. Histologically it is characterized by a marked predominance of benign-appearing spindled cells encasing nodules of embryonal-appearing epithelium. The epithelial component in nephrogenic adenoma consists of multifocal nests of immature epithelium similar to the hyperplastic nephrogenic rests (nephroblastomatosis) associated with Wilms tumor. Two of the five nephrogenic adenomas contained associated low-grade papillary adenocarcinomas. BMEST lacks any immature renal epithelial tissue or low-grade papillary carcinoma. Moreover, the stroma of the nephrogenic adenoma lacks any actin or desmin positivity, a feature present in the ovarian-like stroma of our case. The finding of the dilated ducts with hobnailed epithelium set in the spindle cell stroma (Fig. lB) raises the possibility of a relationship of our case with cystic nephroma. In comparison with cystic nephroma, however, we did not find in our case any immature embryonal renal tissue, heterologous stromal structures and most importantly, no cystic appearance. It cannot be excluded, however, that our case represents a solid variant of "cystic" nephroma, an entity not yet recognized in any classification. The location in the renal parenchyma and absence of the transitional
448 . M. Michal and M. Syrucek urothelial epithelium clearly distinguishes the BMEST from the recently described cystic hamartoma of the renal pelvis [9]. The lack of mitoses and atypias as well as the low level of proliferation as revealed by MIB I antibody distinguishes the BMEST from the sarcomatoid carcinoma of the kidney.
Acknowledgement: I am most grateful to Dr. Mukensnabl for preparing the figures for this publication, and to the Plzen laboratory staff for their expertise, in particular Mrs. Jana Adamcova. Mrs. Vaclava Winterova is also kindly acknowledged for assistance in typing the manuscript.
2. 3.
4.
5.
Editorial Adendum: The editors would like to note that one of the referees found the tumor presented here to show a considerable similarity to a condition outlined as a "solitary multilocular cyst of the kidney" (segmental cystic disease with the synonyms multilocular cystic nephroma, polycystic nephroma, differentiated nephroblastoma, lymphangioma and papillary cystadenoma) by Bennington and Beckwith [1]. 1. Bennington JL, Beckwith JB (975) Atlas of Tumor Pathology; Tumors of the Kidney, Renal Pelvis, and Ureter. Second Series, Fascicle 12, Repritned 1983, pp 84-85. Armed Forces Institute of Pathology, Washington, D.C.
6. 7.
8.
9.
the pancreas. Morphologic and immunohistochemical observations. Am J Surg Pathol11: 11-20 Block NL, Grabstad HG, Melamed MR (1973) Congenital mesoblastic nephroma (leiomyomatous hamartoma): First adult case. J Urol110: 380-383 Compagno J, Oertel JE (978) Mucinous cystic neoplasms of the pancreas with overt and latent malignancy (cystadenocarcinoma and cystadenoma). A clinicopathologic study of 41 cases. Am J Clin Pathol69: 573-588 Devaney K, Goodman ZD, Ishak KG (994) Hepatobiliary cystadenoma and cystadenocarcinoma. A light microscopic and immunohistochemical study of 70 patients. Am J Surg Pathol18: 1078-2091 Durham JR, Bostwick DG, Farrow GM, Ohorodnik JM (1993) Mesoblastic nephroma of adulthood. Report of three cases. Am J Surg Pathol 17: 1029-1038 Hennigar RA, Beckwith BJ (992) Nephrogenic adenofibroma. A novel kidney tumor of young people. Am J Surg Pathol16: 325-334 Murphy MW, Beckwith JB, Farrow GM (994) Tumors of the kidney, bladder and related urinary structures. Atlas of tumor pathology, fascicle 11, third series. Armed Forces Institute of Pathology, Washington, D.C. Lastaria D, Sachdev RK, Babury RA, YU HM, Nuovo GJ (990) Immunohitochemical analysis for desmin in normal and neoplastic ovarian stromal tissue. Arch Pathol Lab Med 114: 502-505 Pawade J, Soosay GN, Delprado W, Parkinson MC, Rode J (1993) Cystic hamartoma of the renal pelvis. Am J Surg Pathol17: 1169-1175
References I. Albores-Saavedra J, Angeles-Angeles A, Nadji M, Henson DE, Alvarez L (987) Mucinous cystadenocarcinoma of
Received: September 23, 1996 Accepted in revised form: April 16, 1997