Yes-associated protein 1 (YAP1) expression in adenoid cystic carcinoma of the lacrimal gland.

PURPOSE: To characterize nuclear expression of Yes-associated protein 1 (YAP1), a key effector of the Hippo pathway, in lacrimal gland adenoid cystic carcinoma (LG ACC) and explore potential associations with clinicopathologic features and clinical outcomes. METHODS: A retrospective, multi-institutional study of 24 LG ACC specimens was performed. Immunohistochemistry (IHC) was used to assess nuclear YAP1 expression. Staining intensity and percentage expression were combined into a composite NY-SCORE. Exploratory analyses evaluated relationships between YAP1 expression scores, clinicopathologic features, and clinical outcomes. RESULTS: Nuclear YAP1 expression was observed in all 24 LG ACC cases: 6 tumors showed moderate staining (NY-SCORE 5-6), 18 tumors showed high staining (NY-SCORE 7-8), and none were low-scoring. Exploratory analyses did not demonstrate statistically significant associations between YAP1 expression and clinicopathologic features or clinical outcomes. CONCLUSIONS: Nuclear YAP1 expression was consistently present in LG ACC tissue, suggesting that YAP1 nuclear localization is a common feature of this malignancy and supports future investigation of Hippo pathway activation in LG ACC. While YAP1 expression did not distinguish clinicopathologic risk or outcomes in this cohort, its uniform presence provides a foundation for future studies evaluating its biological role and potential therapeutic relevance.