ESR1 and triple-negative breast carcinoma: Low-grade adenosquamous carcinoma (LGASC) is a rare MBC that occurs in the breast parenchyma and has more favorable prognostic characteristics than other metaplastic carcinomas.[3] Although most LGASC patients present with the triple-negative breast cancer (TNBC) subtype, isolated instances of ER-positive (estrogen receptor) patients have been documented, suggesting potential variations in treatment options.[4,5]