Ameloblastoma in young persons: a clinicopathologic analysis and etiologic investigation

Ameloblastoma, an odontogenic tumor of ectodermal origin, has been reported to arise, on rare occasions, in a primordial or dentigerous cyst of a young person. Numerous authors have suggested differing nomenclatures for these ameloblastomas (e.g., mural, unicystic, monocystic, intracystic, cystogenic, cystic, plexiform unicystic) and have sought to describe and classify the clinical and histopathologic features. These tumors have been characterized as a distinct variant exhibiting less aggressive behavior and a lower rate of recurrence than conventional ameloblastoma. Furthermore, various etiologic factors have been proposed for these cystic ameloblastomas, including (1) nonspecific irritational factors such as extraction, caries, trauma, infection, inflammation, or tooth eruption; (2) nutritional deficit disorders, and (3) viral infection. The files of the combined accessioned cases of Emory University's and Temple University's oral pathology laboratories were searched and a review of the literature was performed. Thirty-eight cases of mandibular ameloblastoma (37 intraosseous, 1 peripheral) in persons 19-year-old and younger were found from a combined total of 311 accessioned cases of ameloblastoma (12.2%). The average age at diagnosis was 10.4 years for the 18 males and 20 females. Of the 33 cases in which race was stated, 19 (57.6%) were white and 14 (42.4%) were black. In the 28 cases in which a clinical diagnosis was offered, fifteen (53.6%) were thought to be dentigerous cysts. Ten cases from patients less than 19 years old were investigated by means of an immunohistochemical staining technique for the detection of human papilloma virus (HPV) genus-specific structural antigen in formalin-fixed, paraffin-embedded tissue. Three of the ten cases (cases 31, 37 and 38) were positive for HPV capsid antigen, whereas none of ten randomly selected ameloblastomas in adults was positive. A discussion of the clinical and histopathologic comparative findings, with emphasis on treatment results and possible HPV etiology, is included. The preliminary nature of finding HPV in the tumor cells is stressed, with recommendation for further verification and typing with the more sensitive in situ hybridization technique.