Clinicopathological and immunohistochemical characteristics of papillary renal cell carcinoma with emphasis on subtyping.

Papillary renal cell carcinoma (PRCC), a morphologically and genetically distinct subtype of RCC, is morphologically separated into 2 subtypes for therapeutic and prognostic purposes. Type 2 tumors are generally believed to have a poorer prognosis than type 1 tumors. In spite of multiple studies, many clinicopathological issues about PRCC remain vague. We studied the clinicopathological features associated with type 1 versus type 2 PRCC, and we compared the immunohistochemical profiles in both subtypes of PRCC. We identified a total of 144 cases (74 type 1, 46 type 2, and 24 mixed), 29 female and 115 male. Mean age was 56 years for type 1 and 59 years for type 2. Mean tumor size was 3.6 cm for type 1 and 4.6 cm for type 2. Type 1 tumors were more likely to have nuclear grade 2 and less, whereas type 2 tumors were more likely to have nuclear grade 3 and above (P = .0001). There was no significant association between tumor type and renal sinus fat invasion, invasion of muscular branches of renal vein, perinephric fat invasion, microvascular angiolymphatic invasion, and main renal vein invasion. Type 2 tumors have higher nuclear grades than type 1 tumors. Based on long follow-up data, both subtypes appear to have excellent prognosis when diagnosed at early stage. The immunohistochemical profiles of both types 1 and 2 PRCC are essentially the same. The similar immunohistochemical profile suggests that PRCC is one entity with divergent histologic features.