spindle cell variant of ameloblastic carcinoma arising from an unicystic amelobastoma: report of a rare case

malignant transformation of ameloblastomas arising from an odontogenic cyst or de novo is wellrecognized. malignancies in ameloblastomas may involve metastasis or a local dysplastic change in the tissue. the latter are classified as ameloblastic carcinomas. a 75-year-old male presented with a mandibular cystic swelling, with no evidence of metastasis. dysplastic ameloblastic cells with spindlecell transformation were seen arising from a cystic lining with features of a unicystic ameloblastoma. immunohistochemically the lesion stained positive with cytokeratin 8,19 and alpha smooth muscle actin, but was negative for vimentin. a diagnosis of spindle-cell ameloblastic carcinoma was made. spindle-cell ameloblastic carcinomas are rare and this is the second case arising from a unicystic ameloblastoma reported in literature. the recognition of this transformation and inclusion of this entity in the classification of ameloblastic carcinomas is stressed. key words: ameloblastic carcinoma, ameloblastoma, odontogenic carcinoma, spindle-cell transformation, unicystic ameloblastoma