TRPS1 Function Beyond Breast: A Retrospective Immunohistochemical Study on Non-breast Cytology Specimens

AbstractIntroductionTrichorhinophalangeal syndrome type 1 (TRPS1) has emerged as a reliable immunohistochemistry (IHC) marker for identifying breast origin in metastatic carcinomas. This study investigates the utility of TRPS1 IHC in non‐breast cytology specimens.Materials and MethodsA retrospective search of our pathology database for the year 2021 identified fluids (pleural and peritoneal) and liver, lung and bone fine needle aspirations (FNAs) with surgical follow‐up confirming non‐breast metastatic carcinomas. Cell blocks from cases with sufficient neoplastic cells underwent immunostaining using a rabbit polyclonal antibody against human TRPS1. Cases lacking tumor on deeper levels after the original work‐up were excluded from the study. Two pathologists independently interpreted the TRPS1 staining.ResultsOf 136 cases assessed, 31 (22.79%) exhibited positive TRPS1 staining, while 105 (77.21%) were nonreactive. Positivity rates were observed in tumors of Mullerian cell origin, gastrointestinal tract (GIT), and lung origin at 28.85%, 25%, and 21.57%, respectively. Of the tumors of Mullerian cell origin 10 (66.67%) were serous carcinomas, 4 (26.67%) were endometrioid carcinomas, and one (6.67%) was a clear cell carcinoma. Lung tumors comprised seven (63.64%) squamous cell carcinomas and four (36.36%) adenocarcinomas, while the gastrointestinal tumors consisted of 14 (80%) adenocarcinomas and one (20%) squamous cell carcinoma.ConclusionsAlthough recognized as a sensitive marker for mammary carcinomas, TRPS1 immunostaining was also detected in Mullerian, lung, and GIT carcinomas. This highlights the significance of being cautious when depending solely on TRPS1 immunostaining to distinguish metastatic breast tumors.