OBJECTIVETo study the morphologic characteristics and prognostic significance of 2 histologic subtypes of papillary renal cell carcinoma (PRCC).

METHODSA series of 48 tumors previously diagnosed as PRCC during the period from 2003 to 2013 were evaluated. All available slides were reviewed and 39 cases were confirmed to be PRCC. The detailed histomorphologic features were evaluated. The tumors were subtyped using the WHO classification and a novel mechanism suggested in recent literature, with prognostic correlation. Type 1 PRCC was assigned for tumors demonstrating simple cuboidal epithelium, irrespective of nuclear grade or other histomorphologic features. Tumors demonstrating cellular pseudostratification and high-grade nuclei were classified as type 2 PRCC.

RESULTSThe novel subtyping mechanism was more practical and correlated with the outcome of patients. The scope of type 1 PRCC was expanded. Type 2 PRCC demonstrated high tumor stage and high nuclear grade, and was more likely to have perinephric/renal sinus fat invasion and sarcomatoid differentiation. Follow-up information was available in 32 patients, including 4 deaths in patients haboring type 2 PRCC. The survival rate of patients with type 2 PRCC was significantly lower than that of type 1 PRCC.

CONCLUSIONSThe novel subtyping mechanism is more practical than WHO classification. Type 1 and type 2 PRCCs share many overlapping histomorphologic features. Type 2 PRCC is notably associated with worse prognosis. Recognizing the histomorphologic diversity of PRCC and classifying subtypes accurately are important in predicting the prognosis of patients with PRCC.