Cytologic diagnosis of solid acinic cell carcinoma of salivary gland

Objective: Acinic cell carcinoma (ACC) of the salivary gland is difficult to diagnose cytologically because it shows variable morphology, resembles normal acinic cells, and seldom contains atypical cells. Study Design: We studied the architecture of ACC cell clusters and tumor cells, and compared its cytological features with histopathological findings. Results: Cytomorphologically, cell clusters were classified as acinar, rosette-like, ductal, pseudopapillary, and adhering to capillary blood vessels. Histologically, all tumors were diagnosed as solid ACC, but some tumor cells formed glandular lumina. At the cyst sites, tumor cells showed papillary proliferation in the lumina. Immunohistochemically, amylase staining was positive, and CD34 staining highlighted numerous capillary vessels. Ki-67 staining was positive in less than 5% of primary tumors and 10% of recurrent tumors. Conclusion: Observation of the 5 types of tumor cell clusters we examined is of great help in diagnosing ACC. In cytologic examination, it is important to assess tumor cell appearance, cell cluster structure, and features of cells composing clusters rather than individual cell characteristics.