Ameloblastic carcinoma (secondary type) with extensive squamous differentiation areas and dedifferentiated regions.

Ameloblastic carcinoma is rare, accounting for 1.5%-2.0% of all odontogenic tumors. Few small series are available, but data on its clinicopathologic characteristics derive mainly from single case reports; therefore, descriptions of new cases may help to better understand the biological characteristics of this rare odontogenic malignancy. In the current report we describe an ameloblastic carcinoma affecting a 27-year-old female patient who had a previous diagnosis of ameloblastoma 7 years before. The carcinoma featured extensive areas of squamous differentiation resembling a primary intraosseous squamous cell carcinoma, as well as areas of dedifferentiation, a poorly documented histologic characteristic of ameloblastic carcinoma. This case provides new insights on the microscopic spectrum of ameloblastic carcinoma, permitting a critical discussion of the current World Health Organization classification of this odontogenic tumor.