Clinicopathological features of salivary and non-salivary adenoid cystic carcinomas

Adenoid cystic carcinoma (ACC), commonly from salivary glands, is known for its insidious local growth and usually protracted clinical course. ACC developing from non-salivary glands (i.e., non-salivary ACC) is heterogeneous, and its clinicopathological features remain poorly defined. Patients treated for ACC in a single institution between 1995 and 2007 were included in this study. Immunohistochemical evaluation of Ki-67, E-cadherin, p16, and cyclinD1 was performed. The prognostic significance of clinical and immunophenotypic markers was evaluated. 83 cases of salivary ACC and 24 cases of non-salivary ACC were included. The expression levels of Ki-67 (54.8%), E-cadherin (90.4%), p16 (32.9%), and cyclinD1 (19.2%) between ACCs present at various sites were not different. Sinonasal, lacrimal, and tracheobronchial ACCs had significantly worse outcomes than those of ACC of the major salivary glands. Postoperative radiotherapy reduced the recurrence rate of patients with a negative resection margin (P = 0.028). Older age (age >60 years), advanced stage, positive resection margin, high histological grade, and high expression of Ki-67 were significantly correlated with poor prognosis. In conclusion, the site of origin plays a role in the prognosis of ACC, in which positive resection margin and advanced stage are possible factors underlying the differences in outcomes.