Papilliferous keratoameloblastoma of mandible: a papillary ameloblastic carcinoma: report of a case with a 6-year follow-up and review of the literature.

We report a fourth case of papilliferous keratoameloblastoma, with a 6-year follow-up. A 62-year-old man underwent resection of a right mandibular neoplasm infiltrating bone and soft tissues. Microscopically, there were cysts lined by papillary projections and containing necrotic debris. Cribriform, solid, and tubular patterns were also present. No regional or distant metastases were found. A local recurrence, developed 3 years later, showed a predominance of the lesser differentiated patterns and focal granular cell ameloblastomatous features. The patient died soon after surgery of unrelated causes, with a further local relapse. The tumor coexpressed cytokeratins and vimentin, and S100 protein (the latter focally in the relapse). It was instead unreactive for Alcian blue, actin, maspin, and GFAP. We suggest that papilliferous keratoameloblastoma be renamed "papillary ameloblastic carcinoma."