Papillary renal cell carcinoma is the second most frequent malignant neoplasm of the adult kidney. It accounts for 10 -15% of all renal carcinomas (1). Papillary renal cell carcinoma is now a wellestablished entity with specific morphological, immunohistochemical, and cytogenetic features. Classical prognostic factors used for renal carcinomas are the TNM stage and the Fuhrman grade. Usually, papillary renal cell carcinoma has been considered to have a better prognosis than clear renal cell carcinoma (1-2). Delahunt and Eble (3) have proposed to divide papillary renal cell carcinomas in two morphological types. Type 1 tumor is characterized by small cuboidal cells covering thin papillae with a single line of uniform nuclei and small nucleoli. In Type 2 tumors, the papillae are covered by large eosinophilic cells with pleomorphic nuclei, prominent nucleoli, and nuclear pseudostratification (3). Recently studying a series of 66 cases, Delahunt et al. (4) showed that this morphologic subtyping is an independent predictive factor of outcome. Indeed, Type 2 was associated with a significantly higher Fuhrman grade and a poorer prognosis (4). MUC1 is a large transmembrane glycoprotein expressed in many normal and tumor epithelial cells. MUC1 is frequently overexpressed in carcinoma and is associated with tumor progression and poorer prognosis (5-6). In clear renal cell carcinoma, MUC1 is overexpressed, and the level of expression is associated with the Fuhrman grade and with the tumor progression (7-9).The current study was performed to investigate the prognostic value of histologic typing in papillary renal cell carcinoma and to evaluate the expression of MUC1 in the two types.