Papillary renal cell carcinoma (papRCC) is the most common non clear cell RCC (ccRCC), accounting for 15% to 20% of all RCCs [1,2]. In order to classify papRCC, Delahunt and Eble described 2 major subtypes, which based on histomorphological and structural features of tumor cells [3]. Type 1 papRCC is composed of thin papillae and tubular structures those were lined by small cells with scanty basophilic cytoplasm containing small and oval nuclei and insuspicious nucleoli. The infiltration of foamy macrophages on papillae and psammoma bodies were also typical in type 1. On the other hand, type 2 papRCC comprised papillae being covered with large cells with voluminous eosinophilic cytoplasm characterized by spherical nuclei with pseudostratification and prominent nucloeli.

The use of this histomorphological subtyping was confirmed by World Health Organization (WHO) 2004 Classification [4]. It was endorsed by 2014 International Society of Urological Pathology (ISUP) and 2016 WHO classifications [5,6]. Despite its wide adoption by both pathologists and urologists, approximately one third of papRCC cases could not classified into type 1 or type 2. The vast majority of these cases demonstrated overlapping features of 2 subtypes, and were usually assessed as mixed papRCC [7,8].

The prognostic role of histomorphological subtyping on oncological outcomes was an ongoing issue of debate in papRCC due to controversial outcomes reported in the literature since its first description [3]. Accordingly, some studies suggested subtype 2 as a poor prognostic factor, while others reported no prognostic difference between 2 subtypes [7], [8], [9], [10]. The vast majority of these studies were reported by a single institutional experience with relatively small cohorts.

The current 5th WHO classification for urinary and male genital tumors eliminated the histomorphological subtyping in papRCC. However, the experience on prognosis gained from previous histomorphological subtyping for more than 2 decades might be useful on the way of the standardization of fifth WHO classification on renal tumors, globally.

Accordingly, in this multi-institutional study with a large dataset, we aimed to investigate the role of histomorphogical subtyping on prognosis of patients undergoing curative surgery for nonmetastatic papRCC.