Ductal papilloma is an extremely rare benign tumor characterized by localized papillary growth in the salivary ducts, and was previously divided into three tumor types: inverted ductal papilloma, intraductal papilloma, and papillary salivary gland adenoma. In the latest classification (2017), inverted ductal papilloma and intraductal papilloma are recognized as subtypes of ductal papilloma. Herein we report a case of inverted ductal papilloma presenting a mucocele-like mass in the buccal mucosa. The patient was a 63-year-old man. He was referred to our department for close inspection and treatment. An elastic, moderately soft, movable, and incompressible mass of about 5 mm was palpated just below the left buccal mucosa. An excisional biopsy was performed under local anesthesia. Histologically, squamous-like cells and basal cell-like cells showed alveolar-like and papillary-like proliferation inward, contiguous with coated squamous cells. The immunohistochemical stainings were CK7 (+), CK5/6 (+), p63 (+), α-SMA (-), p53 (+), and Ki67 (luminal cells 1.29％, non-luminal cells 5.53%). A diagnosis of inverted ductal papilloma was made. HPV DNA testing returned negative. The lesion was totally removed with no remaining lesion noted in surrounding tissues. In the four years since the operation there has been no recurrence and the patient is doing well.
