Inverted ductal papilloma: report of a rare case and review of the literature.

Inverted ductal papilloma is an uncommon benign papillary endophytic tumor. This report aimed to present a case of inverted ductal papilloma of the oral cavity. A 54-year-old female patient presented with an asymptomatic nodular lesion on the lower lip. Time of duration was undetermined. The diagnostic hypotheses were fibrous hyperplasia and benign mesenchymal neoplasm. An excisional biopsy was performed, and microscopic examination showed an endophytic proliferation of squamous cells with the presence of microcysts, and goblet cells arranged in nest and islands. No cellular atypia was observed. The neoplastic cells were positive for CK7, and CK14. Proliferation index, demonstrated by Ki-67, was positively restricted to the basal tumor layer. The final diagnosis was oral inverted ductal papilloma. No signs of recurrence were found after surgery. Inverted papilloma, intraductal papilloma, oral papilloma.