Spindle cell variant of ameloblastic carcinoma arising from an unicystic amelobastoma: Report of a rare case

Abstract

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