TRPS1 is a valuable addition to the pathologist’s diagnostic toolkit, demonstrating a high sensitivity for breast carcinoma, though with a lower specificity due to its expression in other tumors such as salivary gland tumors, prostate carcinoma, endometrial carcinoma, ovarian carcinoma, gastric carcinoma, synovial sarcoma, and osteosarcoma. The gene discussed is TRPS1; the disease is endometrial carcinoma.