Primary Renal Synovial Sarcoma Confirmed by Cytogenetic Analysis: A Lesion Distinct From Sarcomatoid Renal Cell Carcinoma

Archives of Pathology & Laboratory Medicine, Feb 2005 by Shannon, Beverley A, Murch, Ashleigh, Cohen, Ronald J

* Primary synovial sarcoma rarely originates in the renal parenchyma. When this occurs, origin of this unusual tumor type has been the subject of debate in the literature, with a suggestion that previously reported cases may be more correctly described as renal cell carcinoma with sarcomatoid dedifferentiation. Synovial sarcoma and sarcomatoid renal cell carcinoma may be indistinguishable on pure histologie and immunohistochemical grounds, but these tumors contain distinctly different sets of chromosomal abnormalities. Most previous cases of primary renal synovial sarcoma were confirmed by molecular biology techniques, which detected the SYT-SSX gene fusion transcript typical of this tumor, but no details of the other chromosomal anomalies have been published. We report a case of primary renal synovial sarcoma confirmed by standard cytogenetic analysis, showing the characteristic t(X; 18)(p11.2:q11.2) translocation and other chromosomal aberrations that are typical of synovial sarcoma as opposed to sarcomatoid renal cell carcinoma.

(Arch Pathol Lab Med. 2005;129:238-240)

Primary renal synovial sarcoma is a rare tumor type first described in 1999(1) and further characterized by 2 separate studies in 2000.2,3 Many of these tumors were initially diagnosed as embryonal sarcoma of the kidney or adult Wilms tumor but were subsequently found to harbor the t(X;18)(p11.2:q11.2) translocation that is specific for synovial sarcoma (SS).4 Although SS is most commonly found adjacent to joints and tendons in the limbs of children and young adults, this tumor type has occasionally been identified in more uncommon sites, including head and neck, lung, heart, peritoneum, and prostate.4 To date, there are 16 cases of genetically confirmed primary renal SS reported in the English-language literature. More recently, however, some doubts have been raised as to whether these tumors should be more correctly classified as sarcomatoid renal cell carcinomas (SRCCs).5 The argument for this classification is based on the fact that mixed malignant renal tumors have historically been designated as adenocarcinomas with divergent sarcomatoid differentiation (sarcomatoid carcinoma).5 In contrast, SSs are generally thought to arise from mesenchymal stem cells capable of stromal and/or epithelial differentiation.4

If primary renal SS is indeed a form of sarcomatoid differentiation that arises from renal cell carcinoma (RCC), then it is reasonable to expect that the t(X;18)(p11.2:q11.2) translocation associated with the SS phenotype would occur within a cytogenetic profile characteristic of the underlying RCC subtype. Fifteen of the 16 previous cases of primary renal SS were diagnosed using reverse-transcription polymerase chain reaction to detect the SYT-SSX gene fusion transcript caused by the t(X;18) translocation,2,3 whereas in the one remaining case a t(X;18) translocation was identified by cytogenetic analysis but no further karyotypic details were published.2 Therefore, the background cytogenetic profile of these tumors was unknown. VVe present a case of primary renal SS assessed by standard cytogenetic analysis, which confirms a karyotype that is characteristic of SS as opposed to RCC with or without further genetic aberrations.

REPORT OF A CASE

Following an episode of macroscopic hematuria, a 60-year-old man underwent radical nephrectomy for a radiologically confirmed right-sided renal mass. After receipt of the pathology report, computed tomograms of the chest, abdomen, and pelvis showed no other lesions or evidence of metastatic disease. The patient made an uneventful recovery but developed pulmonary metastases 6 months later. Despite an initial response to chemotherapy, which included imatinib plus 5 cycles of alternating vincristine, adriamycin, and cyclophosphamide or cisplatinum and etoposide, he died 12 months after initial diagnosis.

MATERIALS AND METHODS

Routine tumor samples were fixed in 4% buffered formaldehyde and embedded in paraffin wax. Four-micrometer sections were assessed by routine hematoxylin-eosin stains and immunostains for vimentin (3B4, 1:50; Dako Corporation, Carpinteria, CaIiO, cytokeratin (AE1/AE3, 1:50, and CAM 5.2, 1:100; Dako), desmin (D33, 1:100; Dako), S100 protein (Z0311, 1:100; Dako), and CD117 (c-Kit) (M7140, 1:100; Dako). A fresh tumor sample was subjected to routine cytogenetic analysis.6 Chromosome analyses were conducted on 20 G-banded metaphases.

RESULTS

Gross and Microscopic Findings

A 38 � 29 � 32-mm, ill-defined tumor mass was identified in the renal medulla. The tumor was associated with an area of central necrosis and extended focally into the renal pelvis, which contained an abundant blood clot (Figure 1). Histologie examination revealed a hypercellular monomorphic sarcoma composed of fascicles of spindle cells (Figure 2). No evidence of epithelial differentiation was noted. Mitotic activity was high, with 3 to 5 mitotic figures per high-power field. Tumor infiltration of the renal pelvis and renal parenchyma was noted, along with extension through the renal capsule into the renal sinus and invasion into the main renal vein.