Utility of TRPS1 immunohistochemistry in confirming breast carcinoma: Emphasis on staining in triple-negative breast cancers and gynecologic tumors.

OBJECTIVES:Our aim was to explore the performance of TRPS1 as an immunohistochemical diagnostic marker; find the optimal conditions for its use in breast carcinomas, especially triple-negative breast cancers (TNBCs); and compare its results in carcinomas of a select few organ sites, with an emphasis on gynecologic tumors. METHODS:Tissue microarrays from breast carcinomas (n = 197), endometrial adenocarcinomas (n = 69), ovarian tumors (n = 250), vulvar squamous cell carcinomas (n = 97), pancreatic ductal adenocarcinomas (n = 20), and gastric adenocarcinomas (n = 12) were stained with TRPS1 using 2 different conditions (protocol 1: high pH; protocol 2: low pH). Breast carcinomas consisted of hormone receptor (HR)-positive/ERBB2 (formerly HER2 or HER2/neu)-negative (n = 53) samples, HR-positive/ERBB2-positive (n = 6) samples, and TNBCs (n = 138). RESULTS:Comparing TRPS1 results in breast carcinomas vs tumors from other organ sites, the sensitivity of TRPS1 was 91% and 87%, respectively, while the specificity was 66% and 74% for protocol 1 and 2, respectively. For TNBCs vs gynecologic tumors, the sensitivity of TRPS1 was 89% and 85%, respectively, while the specificity was 65% and 73%, respectively. CONCLUSIONS:TRPS1 stains approximately 90% of breast carcinomas but also up to 71% of endometrial carcinomas, albeit with a weaker median expression. Our data show that although TRPS1 is a highly sensitive marker for TNBCs, it is not as highly specific as previously reported.