A number of recently described renal tumor entities share an eosinophilic/oncocytic morphology, somewhat solid architectural growth pattern, and tendency to present as low-stage tumors. The vast majority of such tumors follow a non-aggressive clinical behavior. In this review, we discuss the morphological, immunohistochemical, and molecular genetic profiles of the three most recent novel/emerging renal entities associated with TSC/mTOR pathway mutations. These are eosinophilic solid and cystic renal cell carcinoma, eosinophilic vacuolated tumors, and low-grade oncocytic tumors, which belong to a heterogeneous group of renal tumors, demonstrating mostly solid architecture, eosinophilic/oncocytic cytoplasm, and overlapping morphological and immunohistochemical features between renal oncocytoma and chromophobe renal cell carcinoma. All three tumors also share a molecular genetic background with mutations in the mTORC1 pathway (TSC1/TSC2/mTOR/RHEB). Despite the common genetic background, it appears that the tumors with TSC/mTOR mutations represent a diverse group of distinct renal neoplasms.

Department of Pathology Faculty of Medicine in Pilsen University Hospital Pilsen Charles University Prague 30460 Pilsen Czech Republic

Department of Pathology Faculty of Medicine University of British Columbia Royal Columbian Hospital Vancouver BC V3L 3W7 Canada

Department of Urology Faculty of Medicine in Pilsen University Hospital Pilsen Charles University Prague 30599 Pilsen Czech Republic

Histopathology Core Facility Niigata University Faculty of Medicine 1 757 Asahimachi dori Chuo ku Niigata 951 8510 Japan

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