2025 Volume 64 Issue 4 Pages 182-187
Background : We report a case of sarcomatoid urothelial carcinoma (SUC) of the renal pelvis as which needed to be differentiated from renal cell carcinoma (RCC).
Case : A 70-year-old man visited us with the complaints of low back pain and body CT examination revealed a 61-mm mass in the upper pole of the left kidney, lymph node metastases, multiple bone metastases, and multiple lung metastases. Sputum cytology suggested the diagnosis of lung metastasis from a primary renal cell carcinoma. Cytological examination of voided urine revealed large tumor cells with round nuclei and clear nucleoli. Some tumor cells were sarcomatoid cells with spindle-shaped nuclei, while others plasmacytoid cells with eosinophilic cytoplasm. Histological examination showed proliferation of urothelial carcinoma cells having focal sarcomatoid and plasmacytoid features. Immunohistochemically, these cells showed positive staining for p63, CK 7, CD10, and vimentin, and negative staining for PAX-8. Based on the findings, we made the final diagnosis of urothelial carcinoma of the sarcomatoid subtype.
Conclusion : In this case, exclusion of RCC was required on account of the findings of sputum cytology, but the histological features and positive immunohistostaining for p63 and PAX-8 confirmed the diagnosis of SUC of the renal pelvis.
