Case Report: Clinicopathological features of papillary renal neoplasm with reverse polarity: a report of four patients and literature review.

Papillary renal neoplasm with reverse polarity (PRNRP) is an emerging entity with an indolent clinical course. It is histologically characterized by a low-grade papillary neoplasm with apically located nuclei and frequent KRAS mutation. With the limited amount of literature, there is no established association between PRNRP and other diseases. Herein, we report four patients of PRNRP in Hong Kong. The neoplasms are discovered incidentally by radiographic investigations and diagnosed by their classical histopathological features. All patients are noted to have underlying hyperglycaemia en passant. This preliminary observation provides insight into the pathogenesis of this specific type of renal neoplasm.