76 Brier reports
According to some authors, it would often be misdiagnosed’. Antibody to s-100 protein is commonly used and is helpful in the assessment of melanocytic neoplasm. However, it lacks specificity. NKI/C3 and HMB-45 are two monoclonal antibodies also used to demonstrate the melanocytic nature of neoplasms in paraffin-embedded tissues. Although it appears less sensitive than NKI/C3, HMB-$5 is much more specific. Expression of its corresponding antigen is thought to be related to melanin production6. In spite of t h e lesions being amelanotic, the lesions in the present case displayed good immunoreactivity with the three antibodies. In comparison to vitiligo, there are normal numbers of skin melanocytes in case of occulocutaneous albinism so that melanocytic tumours can develop. The immunoreactivity with the t h e e antibodies used provides further evidence of the true melanocytic nature of the neoplasms in this present case.
References 1. Schulze KB,Rapini RP.Duvic M.Malignant melanoma in oculocutaneous albinism (Letter to the Editor). Arch. Dermatol. 1989; 12 5: 1583-1 586. 2. Pehamberger H, Hhigsrnann H, WOEK. Dysplastic nevus syn-
3.
4.
5. 6.
drome with multiple primary amelanoticmelanomas in oculocutaneous albinism. 1. Am. Acad. Dermatol. 1984; 11; 731-735. Scott MJ, Giacobetti R, Zugerman C. Malignant melanoma with ocdocutaneous albinism (Letter to the Editor). I. Am, Acad. Dermatol. 1982: 7; 684-685. Wood C, Graham D,Willsen J, Strefling A. Albinism and amelanotic melanoma, Occurrence in a child with positive test results for Wroslnase. Arch. Dermafol. 1982: 118; 283-284. Stoll DB,Ruschak P, Kauh Yet aJ. Lentigo maligna in a woman with oculocutaneous albinism. Arch. Dermatol. 1981: 117; 360-361. Colombari R,Bonettl F, Zamboni G et al. Mstrtbution of melanoma specific antibody (HMB-45)in benign and malignant melanocytic tumours. An immunohlstochemical study on p a r a h sections. Vlrchows Arch. [A] 1988: 413; 17-24.
Histopathology 1992. 21, 76-78
BRIEF REPORT
Primary extrarenal Wilms’ tumour: identification of a putative precursor lesion V. R. SARODE, K.SAVITRI , C .K.BANER JEE, K. L.NARASIMHARAO* & A. KHA JURIA Departments of Pathology and “Pediatric Surgeru, Postgraduate Institute of Medical Education and Research, Chandigarh, India Date of submission 2 October 1991 Accepted for publication 5 February 1992
We report a case of primary ttxtrarenal Wilms’ tumour which, on histological examination, revealed a zone of hyalinized blastema adjacent to,and within the tumour capsule. The tumour showed a predominant stromal component. The presence of the hyalinized blastema adjacent to the turnour raises the possibility that some cases of extrarenal Wilms’ tuniour may have a precursor lesion. Keywords: Wilms’ tumour, extrarenal, metanephrogenic blastema Address for correspondence:Dr V.R.Sarode, Department of Pathology, Postgraduate Institute of Medical Education and Research, Chandigarh 160012. India.
Introduction Primary extrarenal Wilms’ tumour is rare, and theories regarding its origin are-inconclusive’. One theory suggests that they arise from ectopic metanephrogenic blastema’. However, the existence of such precursor lesions has never been documented in these tumours. We report a case which showed histological features suggestive of a precursor lesion.
Case report A two-year-old male child presented with a lump in the
abdomen for 2 months. There were no urinary complaints. Physical examination revealed a 15 x 20 cm
Brief reports
77
Figure 1. a A zone of hyallnized blastema composed of well formed tubules lined by round, hyperchromatic cells. €4 & E. x 240. b Tumour capsule showing tubules entrapped within the hyalinized stroma. H & E. x 240.
firm mass occupying the right hypochondrium and epigastrium. Intravenous pyelography revealed normal kidneys and calyceal systems but with medial displacement of the right ureter by the tumour. A diagnosis of extrarenal Wilms’ tumour was made on fine needle aspiration cytology. An immediate pre-operative chemotherapy consisting of vincristine and actinomycin D was administered. At laparotomy there was a well encapsulated tumour which was separate from the kidney. The kidneys were otherwise unremarkable and were not biopsied. The tumour was removed in one piece. The patient was commenced on chemotherapy. PATHOLOGICAL FINDINGS
Gross examination revealed a smooth, well-encapsulated tumour measuring 1 5 x 12 x 9 cm. On serial slicing there was a well circumscribed, fleshy tumour showing areas of haemorrhage. necrosis and myxoid
degeneration. Multiple sections from the tumour were studied. On microscopic examination, adjacent to and within the tumour capsule, there was a zone of hyalinized blastema showing well-formed tubules, many of which were lined by a single layer of round, hyperchromatic cells around distinct basal lamina (Figure la). Extensive hyalinization of stroma with entrapped tubules was a prominent feature (Figure lb). The tumour underlying this zone was demarcated by a fibrous capsule of variable thickness in a major portion of the tumour and was composed predominantly of the stromal component. The cells were oval to spindle, arranged in sheets and fascicles showing skeletal muscle differentiation (Figure 2). No teratomatous component was identied in any of the sections studied.
Discussion The retroperitoneum is the most common site for
78 Brief reports
nephrogenic rest5. In the kidney, they can be superficial or subcapsular and, less commonly,deep or intralobar in location6.Differentiation may be minimal, or prominent with tubular and occasional glomedar formation. The tubules are lined by small, round'to polygonal hyperchromatic cells. Sclerosis may be a prominent feature, and this type is also known as sclerosing metanephric hamartoma5q6. Although by themselves they are not malignant, they have been thought to be putative precursors of Wilms' tumour. The tumour in our case was separate from the kidney. Histologically a zone of hyalinized blastema composed of tubules was seen adjacent to and within the tumour capsule. Some of the tubules were entrapped within the fibrous stroma. The features were consistent with those of a sclerosing metanephrogenic rest5v6. The tumour underlying this zone was composed predominantly of the stromal component. The presence of this hyalinized blastema in proximity to the tumour, raises the possibility that the tumour may have arisen from it. It may be argued that this area represented differentiation in Wilms' tumour. The histological features and location favours the possibility of this being a sclerosing nephrogenic rest. The kidneys were not biopsied and so it is not known whether there were any foci of blastema in them. Extensive sampling of the tumour did not reveal any teratomatous component. Figure 2. Stromal component of the tiimour showing skeletal muscle differentiation. H & E. x 510.
primary extrarenal Wilms' tiunour. Though little is known about their histogenesis, two theories have been suggested. One theory proposes that they arise within terat~masl-~. Even those in which a teratomatous element was not evident were viewed as teratomas with predominant or exclusive nephroblastic component. Others have suggested their origin is from ectopic metanephrogenic blastema'. Ectopic blastema, though rare, is known to occur14. However, the existence of such a precursor lesion in extrarenal Wilms' tumour has never been documented. There is considerable evidence that Wilms' tumours occurring in the kidney arise h m abnormally persistent
References 1. Broecker BH. Caldamone AA, McWilliams NB, Maurer H. Salzberg A. primary extrarenal Wilms' tumor in children. 1. Pediatr. Surg. 1989:24; 1283-1288. 2. Ward SP,Dehner LP. Sacrococcygeal teratoma with Nephroblastoma (WUms' tumor). A variant of extragonadal teratoma in childhood.A histologic and ultrastructuralstudy. Cancer 1974:33; 1355-1 363. 3. Malik T, Mallk G. Mesh G. Retroperitoneal teratoma with Nephroblastic tissue as the main component. Int. Surg. 1967:47; 246249. 4. Sun C,Rdel L, Wright Let al. Immature renal tissue in colonic wall of patient with caudal regression syndrome. Arch. Pathol. Lab. Med. 1986: 110; 653-655. 5. Beckwith JB. Kiviat NB, Bonadio JF. Nephrogenic rest, nephroblastomatosis and pathogenesisof Wilms' tumor. Pedlatr. PathoJ. 1990 10;1-36. 6. Berry PI.Paediatric solid tumours.In Anthony PP. MacSween RNM eds. Recent Advances in Hlstopptholog#:Churchill Llvingstone. 1987: 208-216.
According to some authors, it would often be misdiagnosed’. Antibody to s-100 protein is commonly used and is helpful in the assessment of melanocytic neoplasm. However, it lacks specificity. NKI/C3 and HMB-45 are two monoclonal antibodies also used to demonstrate the melanocytic nature of neoplasms in paraffin-embedded tissues. Although it appears less sensitive than NKI/C3, HMB-$5 is much more specific. Expression of its corresponding antigen is thought to be related to melanin production6. In spite of t h e lesions being amelanotic, the lesions in the present case displayed good immunoreactivity with the three antibodies. In comparison to vitiligo, there are normal numbers of skin melanocytes in case of occulocutaneous albinism so that melanocytic tumours can develop. The immunoreactivity with the t h e e antibodies used provides further evidence of the true melanocytic nature of the neoplasms in this present case.
References 1. Schulze KB,Rapini RP.Duvic M.Malignant melanoma in oculocutaneous albinism (Letter to the Editor). Arch. Dermatol. 1989; 12 5: 1583-1 586. 2. Pehamberger H, Hhigsrnann H, WOEK. Dysplastic nevus syn-
3.
4.
5. 6.
drome with multiple primary amelanoticmelanomas in oculocutaneous albinism. 1. Am. Acad. Dermatol. 1984; 11; 731-735. Scott MJ, Giacobetti R, Zugerman C. Malignant melanoma with ocdocutaneous albinism (Letter to the Editor). I. Am, Acad. Dermatol. 1982: 7; 684-685. Wood C, Graham D,Willsen J, Strefling A. Albinism and amelanotic melanoma, Occurrence in a child with positive test results for Wroslnase. Arch. Dermafol. 1982: 118; 283-284. Stoll DB,Ruschak P, Kauh Yet aJ. Lentigo maligna in a woman with oculocutaneous albinism. Arch. Dermatol. 1981: 117; 360-361. Colombari R,Bonettl F, Zamboni G et al. Mstrtbution of melanoma specific antibody (HMB-45)in benign and malignant melanocytic tumours. An immunohlstochemical study on p a r a h sections. Vlrchows Arch. [A] 1988: 413; 17-24.
Histopathology 1992. 21, 76-78
BRIEF REPORT
Primary extrarenal Wilms’ tumour: identification of a putative precursor lesion V. R. SARODE, K.SAVITRI , C .K.BANER JEE, K. L.NARASIMHARAO* & A. KHA JURIA Departments of Pathology and “Pediatric Surgeru, Postgraduate Institute of Medical Education and Research, Chandigarh, India Date of submission 2 October 1991 Accepted for publication 5 February 1992
We report a case of primary ttxtrarenal Wilms’ tumour which, on histological examination, revealed a zone of hyalinized blastema adjacent to,and within the tumour capsule. The tumour showed a predominant stromal component. The presence of the hyalinized blastema adjacent to the turnour raises the possibility that some cases of extrarenal Wilms’ tuniour may have a precursor lesion. Keywords: Wilms’ tumour, extrarenal, metanephrogenic blastema Address for correspondence:Dr V.R.Sarode, Department of Pathology, Postgraduate Institute of Medical Education and Research, Chandigarh 160012. India.
Introduction Primary extrarenal Wilms’ tumour is rare, and theories regarding its origin are-inconclusive’. One theory suggests that they arise from ectopic metanephrogenic blastema’. However, the existence of such precursor lesions has never been documented in these tumours. We report a case which showed histological features suggestive of a precursor lesion.
Case report A two-year-old male child presented with a lump in the
abdomen for 2 months. There were no urinary complaints. Physical examination revealed a 15 x 20 cm
Brief reports
77
Figure 1. a A zone of hyallnized blastema composed of well formed tubules lined by round, hyperchromatic cells. €4 & E. x 240. b Tumour capsule showing tubules entrapped within the hyalinized stroma. H & E. x 240.
firm mass occupying the right hypochondrium and epigastrium. Intravenous pyelography revealed normal kidneys and calyceal systems but with medial displacement of the right ureter by the tumour. A diagnosis of extrarenal Wilms’ tumour was made on fine needle aspiration cytology. An immediate pre-operative chemotherapy consisting of vincristine and actinomycin D was administered. At laparotomy there was a well encapsulated tumour which was separate from the kidney. The kidneys were otherwise unremarkable and were not biopsied. The tumour was removed in one piece. The patient was commenced on chemotherapy. PATHOLOGICAL FINDINGS
Gross examination revealed a smooth, well-encapsulated tumour measuring 1 5 x 12 x 9 cm. On serial slicing there was a well circumscribed, fleshy tumour showing areas of haemorrhage. necrosis and myxoid
degeneration. Multiple sections from the tumour were studied. On microscopic examination, adjacent to and within the tumour capsule, there was a zone of hyalinized blastema showing well-formed tubules, many of which were lined by a single layer of round, hyperchromatic cells around distinct basal lamina (Figure la). Extensive hyalinization of stroma with entrapped tubules was a prominent feature (Figure lb). The tumour underlying this zone was demarcated by a fibrous capsule of variable thickness in a major portion of the tumour and was composed predominantly of the stromal component. The cells were oval to spindle, arranged in sheets and fascicles showing skeletal muscle differentiation (Figure 2). No teratomatous component was identied in any of the sections studied.
Discussion The retroperitoneum is the most common site for
78 Brief reports
nephrogenic rest5. In the kidney, they can be superficial or subcapsular and, less commonly,deep or intralobar in location6.Differentiation may be minimal, or prominent with tubular and occasional glomedar formation. The tubules are lined by small, round'to polygonal hyperchromatic cells. Sclerosis may be a prominent feature, and this type is also known as sclerosing metanephric hamartoma5q6. Although by themselves they are not malignant, they have been thought to be putative precursors of Wilms' tumour. The tumour in our case was separate from the kidney. Histologically a zone of hyalinized blastema composed of tubules was seen adjacent to and within the tumour capsule. Some of the tubules were entrapped within the fibrous stroma. The features were consistent with those of a sclerosing metanephrogenic rest5v6. The tumour underlying this zone was composed predominantly of the stromal component. The presence of this hyalinized blastema in proximity to the tumour, raises the possibility that the tumour may have arisen from it. It may be argued that this area represented differentiation in Wilms' tumour. The histological features and location favours the possibility of this being a sclerosing nephrogenic rest. The kidneys were not biopsied and so it is not known whether there were any foci of blastema in them. Extensive sampling of the tumour did not reveal any teratomatous component. Figure 2. Stromal component of the tiimour showing skeletal muscle differentiation. H & E. x 510.
primary extrarenal Wilms' tiunour. Though little is known about their histogenesis, two theories have been suggested. One theory proposes that they arise within terat~masl-~. Even those in which a teratomatous element was not evident were viewed as teratomas with predominant or exclusive nephroblastic component. Others have suggested their origin is from ectopic metanephrogenic blastema'. Ectopic blastema, though rare, is known to occur14. However, the existence of such a precursor lesion in extrarenal Wilms' tumour has never been documented. There is considerable evidence that Wilms' tumours occurring in the kidney arise h m abnormally persistent
References 1. Broecker BH. Caldamone AA, McWilliams NB, Maurer H. Salzberg A. primary extrarenal Wilms' tumor in children. 1. Pediatr. Surg. 1989:24; 1283-1288. 2. Ward SP,Dehner LP. Sacrococcygeal teratoma with Nephroblastoma (WUms' tumor). A variant of extragonadal teratoma in childhood.A histologic and ultrastructuralstudy. Cancer 1974:33; 1355-1 363. 3. Malik T, Mallk G. Mesh G. Retroperitoneal teratoma with Nephroblastic tissue as the main component. Int. Surg. 1967:47; 246249. 4. Sun C,Rdel L, Wright Let al. Immature renal tissue in colonic wall of patient with caudal regression syndrome. Arch. Pathol. Lab. Med. 1986: 110; 653-655. 5. Beckwith JB. Kiviat NB, Bonadio JF. Nephrogenic rest, nephroblastomatosis and pathogenesisof Wilms' tumor. Pedlatr. PathoJ. 1990 10;1-36. 6. Berry PI.Paediatric solid tumours.In Anthony PP. MacSween RNM eds. Recent Advances in Hlstopptholog#:Churchill Llvingstone. 1987: 208-216.
