Cytomorphologic comparison of type 1 and type 2 papillary renal cell carcinoma: A retrospective analysis of 28 cases

Papillary renal cell carcinoma (pRCC) is classified as type 1 or type 2 on the basis of histomorphologic features. Type 1 pRCC typically carries a better prognosis, and renal cell carcinoma is often diagnosed by fine-needle aspiration (FNA). Thus, this study was designed to characterize cytomorphologic features present in FNA cases that could be used to discriminate between type 1 and type 2 pRCC.

Electronic records of Indiana University were searched for pRCC FNA cases (2007-2018). Corresponding surgical pathology reports were reviewed to classify patients as having type 1 or type 2 pRCC. FNA slides were reviewed to assess cytomorphologic features (ie, nuclear grade; cell size; cytoplasmic volume and quality; and the presence of single cells, papillary clusters, nuclear grooves, foamy histiocytes, hemosiderin pigment, psammoma bodies, and hyaline globules). A semiquantitative score was assigned to each feature. The nuclear grade was assigned with the World Health Organization/International Society of Urological Pathology grading system. The cytomorphologic features of type 1 and type 2 pRCC were compared.

Sixteen patients with type 1 pRCC and 12 patients with type 2 pRCC were included in the study. Type 2 pRCC had a higher nuclear grade, a higher volume of cytoplasm, and more granular cytoplasm. Type 1 pRCC more frequently had nuclear grooves and clear cytoplasm. The remaining features (ie, cell size, papillary clusters, single cells, foamy histiocytes, hemosiderin pigment, psammoma bodies, and hyaline globules) were not statistically significant.

Nuclear grade, cytoplasmic volume and granularity or clarity, and nuclear grooves are cytomorphologic features that may aid in the distinction between type 1 and type 2 pRCC.