Role of immunohistochemistry and fluorescence in-situ hybridization (FISH) in the diagnosis of spindle and round cell tumors of the kidney

Spindle cell/mesenchymal tumors of the kidney are rare. The diagnosis is supported mainly by the application of ancillary techniques such as immunohistochemistry (IH) and in-situ hybridization (FISH). An accurate diagnosis is essential because early management by complete resection and adjuvant chemotherapy improves the prognosis dramatically. Synovial sarcoma and primitive neuroectodermal tumor/Ewing sarcoma are infrequent malignancies which usually present in soft tissues but rarely in the kidney. The challenge for the pathologists is to histologically differentiate between different types of sarcomas such as PNET/Ewing's sarcoma, sarcomatous dedifferentiated renal cell carcinoma, metastasis, non-Hodgkin's lymphoma, nephroblastoma and angiomyolipoma. Methods: We report from our experience six exemplary rare cases that presented in the kidney as spindle/round cell tumors. Results: We have arrived at the accurate diagnosis after performing a large panel of IH and FISH. Conclusion: In summary we advise an immunohistochemical panel for round/spindle cell tumors of the kidney and for unclear cases we advise to add (FISH) to get the correct diagnosis, as they are completely different regarding surgical approach and post-operative adjuvant therapy.