GATA3 Expression in Solid Vimentin-Negative Eosinophilic Renal Epithelial Tumors—A Comprehensive Study of 48 Tumors

Vimentin-negative solid eosinophilic renal tumors, such as renal oncocytoma, chromophobe renal cell carcinoma (chromophobe RCC), low-grade oncocytic tumor (LOT) of the kidney, and eosinophilic vacuolated tumor (EVT), often present diagnostic challenge to pathologists as they can have significant morphologic overlap. Recent studies have shown that the LOT is consistently positive for GATA3. To test the utility of GATA3 in this potentially challenging diagnostic setting, we investigated GATA3 expression in 48 vimentin-negative solid eosinophilic renal tumors with unequivocal diagnosis, which included 19 LOTs, 3 EVTs, 12 chromophobe RCCs, 11 renal oncocytomas (ROs), and 3 <i>FLCN</i>-mutated renal tumors. GATA3 was at least focally positive in 89% of the LOTs (17/19), 67% of the EVTs (2/3), and 33% of the chromophobe RCCs (4/12) and was negative in all ROs (0/11) and <i>FLCN</i>-mutated renal tumors (0/3). Our study shows that GATA3 can be useful in differentiating between LOT and RO, but it can be focally positive in many tumors of EVT and chromophobe RCC. Therefore, GATA3 could be useful as a panel of immunohistochemical stains that are used in diagnostic algorithm of vimentin-negative solid eosinophilic renal tumors. However, one should not solely rely on GATA3 as vimentin-negative solid eosinophilic renal tumors can have overlapping GATA3 expression.