| Abstract: | Usage of renal mass biopsy has increased in recent years, ranging from selected clinical scenarios to routine implementation in some institutions. Major tasks for the field of diagnostic histopathology include discriminating primary renal cell cancers from other tumors, especially metastases, hematolymphoid tumors, and urothelial carcinoma. Within primary renal cell neoplasms, relevant distinctions include recognizing clear cell papillary renal cell carcinoma, which despite its resemblance to clear cell cancer is nonaggressive, as well as discriminating oncocytoma from chromophobe carcinoma. Helpful immunohistochemical markers include PAX8 for verification of primary renal cell lineage and carbonic anhydrase IX for support of clear cell subtype. Cytokeratin 7 is generally considered the best marker for discriminating oncocytoma from chromophobe renal cell carcinoma, showing only rare positive cells in oncocytoma and greater staining in chromophobe carcinoma. For metastatic tumors, attempting to discriminate clear cell from non-clear cell types may be important for treatment selection. |
