Primary intestinal-type adenocarcinoma of the buccal mucosa: A case report and literature review.

Intestinal-type adenocarcinoma of the primary salivary glands is extremely rare. So far, only 11 cases of primary intestinal-type adenocarcinoma of the oral cavity and major salivary glands have been reported. Two of those tumors arose in the floor of mouth, 7 in the tongue, and 2 in the major salivary glands. However, it has remained unclear whether these tumors are derived from mature salivary glands, and primary intestinal-type adenocarcinoma of the buccal mucosa has not been reported previously. Here, we present the first documented case of primary intestinal-type adenocarcinoma arising in a minor salivary gland of the buccal mucosa. Histopathologically, the tumor resembled a well-differentiated or mucinous colonic adenocarcinoma. Immunohistochemically, the tumor cells were diffusely positive for AE1/AE3, CAM5.2, CK7, SATB2, beta-catenin, p53, Ki-67, MUC2, and MUC5 AC. CK14 and CK20 were positive in some of the tumor cells. CDX2, CA19-9, SP-A, TTF-1, PSA, SMA, p63, and cyclin D1 were negative in the tumor cells. The tumor in the present case may have originated from salivary gland duct epithelium that underwent transformation to phenotypic intestinal-type epithelium. In this very rare case of primary intestinal-type adenocarcinoma of the buccal mucosa, we considered diagnostic markers that could be indicative of mature salivary gland origin.