Needle aspiration cytology of low-grade transitional cell carcinoma of the renal pelvis.

Five cases of histologically confirmed grade 1 papillary transitional cell carcinoma of the renal pelvis investigated by needle aspiration biopsy cytology were reviewed. In all cases the needle aspirates were hypercellular. Abundant benign-appearing urothelial cells in thick clusters, in small aggregates, and singly were seen in two cases. Numerous single and loosely aggregated urothelial cells with cytoplasmic extensions and slightly pleomorphic nuclei were noted in one case. In two patients numerous urothelial fragments of variable sizes showing defined cytoplasm and mildly nuclear pleomorphism were the main cellular findings.