Acinic cell adenocarcinoma. A clinicopathologic analysis of 294 cases.

Two hundred and ninety-four cases of acinic cell adenocarcinoma were reviewed for the purpose of defining the clinical parameters and determining the distribution of the four histomorphologic tissue patterns and five cell types for correlation to biologic behavior. The vast majority occurred in the parotid gland. There was a male predominance and a peak incidence in the third decade of life. The tumors were usually less than 3 cm in diameter and were slow growing. Pain was a common symptom, but was not indicative of prognosis. Nearly one half of the neoplasms exhibited multiple tissue growth patterns, and three fourths of the tumors displayed more than one cell type. The microcystic pattern was seen most frequently, regardless of the biological behavior of the tumors. The well-differentiated acinic cell was the most prevalent cell type except in cases with metastases, where the intercalated-duct cell type was slightly more frequent. Follow-up of 244 cases revealed a recurrence rate of 12%, a metastatic rate of 7.8%, and death rate of 6.1%. Since all histomorphologic patterns and cell types were manifest in tumors which recurred, metastasized, or caused the death of the patients, it seems appropriate to consider these neoplasms as low-grade adenocarcinomas rather than essentially benign with occasional unpredictable malignant behavior.