Abstract
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.
Highlights
Tuberous sclerosis complex (TSC) proteins are important players in regulating the activity of the mammalian target of rapamycin complex 1
Based on the current knowledge, Low-grade oncocytic tumor (LOT) seems to be a new distinct entity that can present in both syndromic and non-syndromic settings
What the exact role of these changes is in the pathogenesis of Eosinophilic Vacuolated Tumor (EVT) or LOT remains to be elucidated by future studies
Summary
Tuberous sclerosis complex (TSC) proteins are important players in regulating the activity of the mammalian target of rapamycin complex 1 (mTORC1). The detailed analysis of previously described TSC-RCC showed morphological and immunohistochemical overlap with the mTORC1 pathway altered sporadic renal tumors. In 2016, Trpkov et al described 16 sporadic cases of ESC-RCC, demonstrating distinct morphological, immunohistochemical, and molecular-genetic features [10]. A great majority of ESC-RCCs are sporadic and occur in non-syndromic settings, while a subset of identical tumors has been documented in patients with TSC. In in thethe initial study by ESC-RCCs predominant diffuse or focal positivity majority of cases, Trpkov et al., LOT was characterized by a typical. A lack seems loss to beof a new distinct entity that as cana present in both syndromic and non-syndromic settings (tumors with the same morphology were described in patients with TSC [25]). LOT is typically a solitary, tumor that shows low stage, and it is associated with
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