A case of adenocarcinoma NOS in the buccal mucosa

Malignant tumors of the salivary gland have a clear tendency to differentiate into glandular systems such as duct formation, but those that do not correspond to any of the other tumor types are diagnosed as adenocarcinoma NOS. We experienced a case of adenocarcinoma NOS that developed in the buccal mucosa. The patient was a 74-year-old man who noticed a tumor on his left buccal mucosa in January 2017, and was seen in January 2018 because of an increasing tendency. Based on imaging findings and histopathological examination, a malignant tumor of the left buccal salivary gland (T1N0M0, adenocarcinoma NOS) was diagnosed. The tumor cells in the surgical specimen consisted of columnar or cuboidal cells exhibiting nucleomegaly and an increased N/C ratio. Calponin, a basal cell lineage marker, was almost negative, and p63 was positive in a few tumor cells. The Ki67 index was as high as 24.8%, and the patient was diagnosed with adenocarcinoma NOS. Four years and seven months after the operation, no recurrence or metastasis has been observed.