Fine needle aspiration of chromophobe renal cell carcinoma

OBJECTIVE: To describe the cytomorphologic findings of chromophobe renal cell carcinoma (CRCC) in order to preoperatively distinguish this rare neoplasm from other primary or secondary tumors arising from the kidney or presenting as retroperitoneal masses. STUDY DESIGN: Clinical data, fine needle aspiration (FNA) and follow-up surgical specimens from 4 patients with CRCC (3 primaries and 1 metastatic to the liver) were reviewed. Electron microscopy was available for 2 histologic specimens. RESULTS: Two tumors (1 primary and 1 metastatic case) were readily identified as CRCC on FNA. The 2 remaining cases were diagnosed as renal cell carcinoma (RCC) consistent with CRCC. All tumors showed aspirates with moderate to high cellularity, with the cells arranged in small clusters and single cells. Neoplastic cells had abundant heterogeneous cytoplasm, a thickened cell membrane, nuclear hyperchromasia, nuclear outline irregularity, significant nuclear size variation, intranuclear inclusions and frequent binucleation. Histology of the 4 renal tumors was characteristic of CRCC, with positivity for Hale's colloidal iron in all cases. Ultrastructurally, characteristic cytoplasmic microvesicles were observed in the 2 cases that we studied. CONCLUSION: In the adequate clinicoradiologic setting, CRCC has distinctive cytologic features that may allow an accurate preoperative FNA diagnosis.