Keratoameloblastoma: A Case Report

Introduction: Keratoameloblastoma is an extremely rare odontogenic tumor characterized loosely by keratinization formation in an ameloblastomatous epithelium.  Since then there have been sixteen cases described in the English literature. However, debate remains whether this is a unique lesion or an extreme variant of acanthomatous ameloblastoma, a well-described variant defined by squamous metaplasia in the stellate reticulum with or without keratinization.¹  Here we present a case of a keratoameloblastoma that we feel supports that this represents a unique lesion.

Case Report: A 23 year old white male was referred from his community dentist for diagnosis and management of pain in the right maxilla associated with a large radioluscent lesion on CBCT without appreciable swelling or expansion on physical exam.  Incisional biopsy obtained revealed a lesion with features of both keratocystic odontogenic tumor (KOT) and ameloblastoma.  MRI and CT obtained for pre-surgical work-up revealed an enhancing, lytic, lobulated soft tissue mass measuring 3.0 x 2.3 x 2.0 cm, associated with unerupted #1’ with evidence of penetration into the lateral wall of the maxilla.  The patient underwent right hemimaxillecatomy and reconstruction with radial forearm free flap. On histological section, the resected lesion demonstrated areas of classic KOT morphology with flat connective tissue epithelial interface, parakeratinized corrugated surface, and hyperchromatic palisaded basal cells.  These areas immediately abutted columnar cells with reverse nuclear polarization surrounding a loose stellate reticulum, classically associated with ameloblastoma. 

Discussion: The authors intend to report additional immunohistochemical staining data, including calretenin staining which is known to be specific for ameloblastoma.² The presence, absence, and pattern of the staining observed in this lesion and its comparison to prior reports in the literature may help to shed some light onto the identity and origins of this rare odontogenic lesion.

References:

1. Sisto J, Olsen, G. Histogenetic relations between keratoameloblastoma and solid variant of odontogenic keratocyst. J Oral Maxillofac Surg 70:860-864, 2012.

2. DeVilliers P, Liu H, Suggs C, Simmons D. Calretinin expression in the differential diagnosis of human ameloblastoma and keratocystic odontogenic tumor.  Am J Surg Pathol 32:256–260, 2008.