Acinic cell carcinoma arising in the buccal mucosa: A case report of specific type of papillary-cystic variant

Acinic cell carcinoma is a rare malignant salivary gland tumor. Most cases of acinic cell carcinoma occur in the parotid gland and acinic cell carcinoma arising in the minor salivary glands is extremely rare; it accounts for 3-16% of cases. Pathologically, it is well known that tumor cellular features can be identified as acinar, intercalated ductal, vacuolated, clear and nonspecific glandular, and architectural patterns of acinic cell carcinoma are divided into four types: solid, microcystic, papillary-cystic and follicular. The papillary-cystic pattern is generally characterized by prominent cystic lumens that are partially filled with papillary epithelial proliferations. We report a case of acinic cell carcinoma arising in the left buccal mucosa of a 45-year-old male. On MRI findings, the tumor showed an oval, solid mass; however, during the surgical operation, a part of the tumor easily raptured by only finger pressure and the contents leaked out. The contents exhibited a grayish-brown color and mud-like consistency. Pathologically, the tumor showed a large cystic space. Some tumor cells included in the luminal side of cyst wall and the tumor cells partially protruded into the luminal space. The mud-like specimen revealed also tumor cells. These tumor cells were identified as typical serous acinar differentiated cells; therefore, the final diagnosis was acinic cell carcinoma with a papillary-cystic growth pattern that consisted of typical acinar cells. We report the details of this specific type of acinic cell carcinoma and discuss the prognostic factors.