Abstract B014: Characterizing two emerging entities in the kidney: Eosinophilic vacuolated tumor (EVT) and low-grade oncocytic tumor (LOT)

Abstract Context: Oncocytomas are rare benign renal tumors that encompass two emerging entities of eosinophilic vacuolated tumor (EVT) and low-grade oncocytic tumor (LOT). EVT is characterized by a solid growth of eosinophilic cells with cytoplasmic vacuolation, prominent nucleoli, and only very focal CK7 expression. LOT is a neoplasm with bland low-grade nuclei, diffuse strong CK7 labelling, and negative (CD117) expression. This study aims to characterize the immunohistochemistry of EVT and LOT through investigation of additional markers.Methodology: A retrospective review was conducted on renal oncocytic tumors (LOT and EVT) diagnosed at Memorial Hermann TMC between 2014 and 2024. Patient data, including age, gender, and tumor characteristics, were extracted from EMR. Specimens were examined for immunohistochemical markers such as CK7, CD117, GATA3, E-cadherin, and PAX8. The study posed minimal risk and was IRB-approved, with all data de-identified and securely stored.Results: Four patients with LOT were identified, comprising 2 females and 2 males, aged between 62 and 88 years, with a median age of 77 years. Histologically, the tumors were well-circumscribed, consisting of sheets and nests of monomorphic oncocytic cells with round to oval nuclei. Immunohistochemical analysis showed cells were diffusely and strongly positive for CK7 and negative for CD117, distinguishing these tumors from oncocytomas. LOT tumor cells were also found to be positive for GATA3, E-cadherin, PAX8, and Succinate dehydrogenase B (SDHB), while negative for vimentin, renal cell carcinoma (RCC), Carbonic anhydrase 9 (CAIX), CD10, and AMACR (P504s). Proliferation index by Ki-67 was low at 1-2%.Conclusion: The study provided detailed insights into the immunohistochemical profile and distinguishing features of LOT. LOT was found to be positive for GATA3 and BerEp4, which are distinct immunohistochemical characteristics compared to other renal oncocytic tumors. which aids in accurate diagnosis and enhances understanding of these emerging entities. Citation Format: Brenda Mai, Phuoc Christie-Nguyen, Rania Moin. Characterizing two emerging entities in the kidney: Eosinophilic vacuolated tumor (EVT) and low-grade oncocytic tumor (LOT) [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Functional and Genomic Precision Medicine in Cancer: Different Perspectives, Common Goals; 2025 Mar 11-13; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85(5 Suppl):Abstract nr B014.