Diagnosis of metastatic renal cell carcinoma on fine-needle aspiration cytology.

Fine-needle aspiration has assumed an increasingly important role in the diagnosis and management of patients with advanced stage cancer. Given its predilection for metastases to distant sites and organs at the time of presentation, metastatic renal cell carcinoma (RCC) is not infrequently encountered in the setting of fine-needle aspiration for initial diagnosis. In some instances, fine-needle aspiration may be the only opportunity to obtain diagnostic tissue to diagnose and subclassify RCC. Therefore, cytopathologists and cytotechnologists should be familiar with and recognize the cytomorphology of RCC and the ancillary studies that can be used to confirm and subclassify RCC. Herein, we describe a case of metastatic RCC initially diagnosed on fine-needle aspiration, discuss the cytomorphologic features of RCC subtypes, and review pertinent ancillary immunohistochemical and cytogenetic adjuncts.