Amyloid-producing ameloblastoma of the maxilla in a 17-year-old cynomolgus macaque (Macacafascicularis).

Amyloid-producing ameloblastomas (APAs) are a histological variant of ameloblastoma in which the neoplastic odontogenic epithelial cells are associated with the production of amyloid. This jaw-associated entity has been only rarely described in animals and purportedly does not exist in humans. This report is the first description of an APA in a primate. A 17-year-old, male, captive cynomolgus macaque (Macaca fascicularis) had a slowly growing mass on the left rostral maxillary region that involved the bone. The mass was first seen in 2022 associated with the left maxillary canine tooth (203) and regrew after incomplete excision and extraction of the affected canine tooth. Additional excision was performed in 2024, at which time the mass was 3.8 cm in diameter, roughly spherical, tan and hard. Histologically, the mass was composed of packets, cords, anastomosing trabeculae and plexiform ribbons of odontogenic epithelial cells embedded in abundant fibrovascular stroma. Packets of epithelial cells surrounded an abundant, apical, congophilic amyloid matrix that was variably mineralized. Odontogenic epithelium was immunoreactive to cytokeratin AE1/AE3 and had no immunoreactivity for vimentin. These findings are diagnostic for APA. This is the first report of APA in any primate, human or non-human, raising the question of whether this entity can occur in humans.