Papillary renal-cell carcinoma: fine-needle aspiration of 15 cases.

Although papillary carcinoma of the kidney is a distinct clinical and pathological entity, there are few descriptions of its cytologic features in the literature. We describe the cytologic features of aspirates from 15 papillary carcinomas of the kidney. The smears showed abundant papillary clusters with vascular cores and relatively few single cells. Tumor cells contained moderate to scant cytoplasm, nuclei were usually small and uniform, mild to moderate hyperchromasia was routine, nucleoli were single and small, and nuclear grooves were often prominent. Histiocytes and psammoma bodies were present in only four cases. Hemosiderin pigment within tumor cells was also present in four cases. Differential diagnosis should consider low-grade transitional-cell carcinoma, metastatic adenocarcinoma, normal renal tubular epithelium, mesothelial cells, and, occasionally, Wilms' tumor. Cytologically recognizing the distinct entity of papillary carcinoma is important in the workup of primary renal neoplasms and metastatic papillary neoplasms of unknown origin.