AN IMMUNOHISTOCHEMICAL STUDY COMPARING CLEAR-CELL SARCOMA OF THE KIDNEY AND WILMS-TUMOR

This study explores immunohistochemical characteristics that may be of diagnostic value in differentiating clear cell sarcoma of the kidney (CCSK) from Wilms' tumor (WT) and may provide some insight into the hi stogenesis of CCSK. Formalin-fixed, paraffin-embedded sections of 8 CC SK and 9 WT were stained, using the standard avidin-biotin peroxidase complex method, for vimentin (VIM), Factor-8 related antigen (F8A), ep ithelial membrane antigen (EMA), desmin (DES), S-100 protein and Mac 3 87. CCSK cells consistently exhibited moderate to strong diffuse cytop lasmic positivity for VIM and were negative for F8A, EMA, DES, S-100 a nd Mac 387. In contrast, only patchy groups of stromal cells and primi tive glomeruloid structures in WT exhibited VIM-positivity. Blastemal cells were VIM-negative. Stromal cells with rhabdomyomatous differenti ation exhibited cytoplasmic positivity for DES. Epithelial cells of ma turing tubular structures showed EMA-positivity whereas immature tubul ar structures were EMA-negative. Neither blastemal, stromal nor epithe lial elements in WT were positive for F8A, S-100 or Mac 387. Podocytes and mesangial cells of glomeruli in 3 mid-trimester human abortuses ( controls) exhibited moderate to strong VIM-positivity. The importance of differentiating CCSK from WT has been repeatedly emphasized because of its poorer prognosis and the necessity of adding Adriamycin to the chemotherapeutic regime. The consistent VIM-positivity of CCSK cells can be a useful feature in differentiating it from ''blastemal-predomi nant'' WT, with which it is often confused. Although vimentin expressi on by CCSK cells is consistent with a mesenchymal character, the possi bility of a histogenetic link with glomerular podocytes or mesangial c ells should also be considered.