Morphologic subtyping of papillary renal cell carcinoma: correlation with prognosis and differential expression of MUC1 between the two subtypes.

Papillary renal cell carcinoma is now a well-established entity with distinct histological and cytogenetic features. A subdivision has been proposed in correlation with prognosis. Type 1 is the most frequent subtype and appears to have a better prognosis than Type 2. The subdivision is based on microscopic criteria. To investigate these 2 types of papillary renal cell carcinoma, we have compared the clinical features, ancillary factors (TNM stage, Fuhrman grade), survival and MUC1 expression in 25 Type 1 and 12 Type 2 papillary renal cell carcinomas. Type 2 tumors were significantly associated with a higher Fuhrman grade (Grade III frequent; P <.001). Type 2 tumors were also associated with a poorer prognosis than Type 1 (P <.005). Fuhrman grade was significantly associated with prognosis (P <.005). The type and the prognosis were not correlated with the TNM stage. We have shown a differential expression of MUC1 between Type 1 and Type 2 with a polarized expression in Type 1 and a rare expression in Type 2. In conclusion we confirm that the morphologic sub-typing and Fuhrman grade are valuable factors of outcome of papillary renal cell carcinomas and that MUC1 immunostaining is useful in differentiating Type 1 and Type 2 tumors.