Demographics, clinical features, and survival of patients with adenoid cystic carcinoma in major and minor salivary glands versus non-salivary sites: an updated SEER analysis.

INTRODUCTION: Adenoid cystic carcinoma (ACC) is a rare malignancy of secretory glands, most commonly arising in the salivary glands but also reported in the lung/bronchus, breast, skin, and other secretory gland tissues. Although typically slow-growing, ACC is also associated with high risk of local recurrence and distant metastases. Population-based studies are necessary to understand site-specific characteristics and clinical outcomes. MATERIALS AND METHODS: We analyzed SEER 17 data from 2009 to 2021 to assess site distribution, demographic and clinical characteristics, and survival among patients with ACC. Frequencies were calculated for common sites, and cause-specific survival (CSS) was evaluated by site and stage. Cox regression was used to identify predictors of survival. RESULTS: A total of 4,294 ACC cases were identified. The most common sites were the major salivary glands (32%), and the collective sites classified as minor salivary glands (36%), while non-salivary gland sites accounted for 32%, including breast (16%), skin (6%), lung/bronchus (5%), and eye/orbit (2%). This represents a small but significant increase in ACC arising at non-salivary sites compared with pre-2009 SEER data (28%). Five-year CSS was high for localized disease (87-99%), moderate for regional disease (57-92%), and poor for distant disease (12-61%). Older age, high tumor grade, large tumor size, and nodal involvement were associated with worse survival. Stage- and site-specific survival patterns were consistent with earlier SEER data. CONCLUSIONS: ACC is a heterogeneous cancer with distinct site-specific features. Survival has remained largely unchanged over the past three decades. Poorer outcomes are associated with older age, high tumor grade, larger tumors, and advanced stage.