Basal cell adenoma is a rare type of benign salivary gland tumour found most commonly in the parotid gland. We present an extremely rare case of basal cell adenoma arising in the minor salivary gland of the upper lip. The patient was a 59-year-old Japanese man who visited our department with a chief complaint of a mass in the upper lip, which had increased in size over several years. A mobile, elastic, relatively soft mass without tenderness was palpable in the upper lip region. The mucosa of the upper lip covering the mass was normal. Tumour extirpation was performed under local anesthesia. Histologically, the tumour had a capsule and was composed of islands of relatively uniform, monotonous cells. Immunohistochemically, the inner tumour comprised tubuloductal structures that showed strong staining for CK7, while the outer tumour showed weak staining for CK7. The outer tumour cells also stained positively for CD10 and p63. The MIB-1 (Ki-67) labeling index was extremely low. Basal cell adenoma was diagnosed based on these results. The postoperative course was uneventful and there has been no recurrence.

Key words : basal cell adenoma; minor salivary gland; upper lip; immunohistochemistry