TRPS1 Immunohistochemistry in Salivary Gland Neoplasms: Analysis on Cytology Cell Blocks and Surgical Follow‐Up Correlation

ABSTRACT Introduction In this study we aim to analyze the TRPS1 immunostaining of salivary gland tumors (SGT) on cytology cell blocks and compare the staining pattern on subsequent surgical resections. Methods Malignant SGTs, oncocytomas and basal cell adenomas diagnosed on fine needle aspiration were retrieved from 2019 to 2021 database. Cases with surgical follow‐up were selected. TRPS1 staining was performed on cytology cell blocks and surgical specimens. Scoring was interpreted by two pathologists independently. Results Our cohort comprised of 58 cases: 45 malignant and 13 benign. TRPS1 scoring was interpreted for 44 cytology and 51 surgical cases. 14 cytology cases lacked tumor cells on deeper levels. For 7 cases, surgical blocks were not retrievable. TRPS1 positivity for cytology and surgical cases were 52% and 47% respectively. In the malignant cohort, TRPS1 was positive in 21/32 (66%) cytology cases and 21/43 (56%) surgical cases. All cases of basal cell adenocarcinoma, carcinoma ex pleomorphic adenoma and salivary duct carcinoma were TRPS1 positive on cytology. All cases of adenoid cystic carcinoma and acinic cell carcinoma were TRPS1 positive on surgical resections. In the benign cohort, TRPS1 was positive in 2/12 (17%) cytology cases; however, none of the surgically resected benign cases showed reactivity (0/8). Cytology‐surgical correlation of TRPS1 staining was done in 37 cases. We found 21 concordant and 16 discordant cases. Discordance was highest in mucoepidermoid carcinoma. Conclusion TRPS1 is not an entirely specific marker for breast carcinoma. TRPS1 positivity was noted in a substantial number of salivary gland malignant neoplasms. Cases demonstrating discordance in TRPS1 staining pattern on cytology‐surgical correlation warrant further exploration.