Acinic cell carcinoma. Clinicopathologic review. The authors reviewed 90 cases of acinic cell carcinoma treated at the Mayo Clinic to assess long-term follow-up and to study features predictive of disease progression. Sixty-three patients (55 females and 35 males) were seen for primary treatment; 27 had recurrent disease when first evaluated. Histologically, these tumors were composed of serous acinar cells and intercalated duct-type cells. Morphologic patterns included solid, microcystic, follicular, and papillary-cystic. All patients were followed for at least 10 years or until death. Of the primary treatment group, 44% had local recurrence, 19% had metastasis, and 25% died of disease. Disease first recurred locally up to 30 years after presentation and resulted in death after as many as 38 years. Poor prognostic features include pain or fixation; gross invasion; microscopic features of desmoplasia, atypia, or increased mitotic activity; and excision as initial treatment. Neither morphologic pattern nor cell composition was a predictive feature. 