SA3 - Are Incisional Biopsies Reliable to Select Definitive Treatment in Patients with Ameloblastoma of the Jaws? A 15-year Interdisciplinary Retrospective Study

Abstract: Ameloblastomas are tumors of odontogenic epithelium that, although benign, can have a locally aggressive course causing significant morbidity. WHO classifies ameloblastomas as 1 of 3 variants: solid/multicystic, unicystic, and peripheral. Resection, the standard treatment, is deemed curative, but can be debilitating to the patient. Unicystic subtype is considered less aggressive and could be treated with enucleation and curettage. The mercurial presentation of ameloblastomas makes the chosen treatment modality essential in decreasing the recurrence rates and associated morbidity. Definitive treatment is chosen based on an incisional biopsy, but a true diagnosis of unicystic ameloblastoma requires the entire specimen. The aim of this study is to assess the potential sampling error with an incisional biopsy and potential consequences on treatment outcomes at long-term follow-up.

This is a retrospective cohort study for patients with ameloblastoma of the jaws treated at the Virginia Commonwealth University Department of Oral and Maxillofacial Surgery between 2005 to 2020. Patients with biopsy-proven ameloblastoma with a minimum of 1-year follow-up after definitive treatment and complete documentation were included. Predictor variables include radiographic findings, incisional biopsy, and histologic samples. Outcome variable is concordance between initial incisional biopsy and final treatment pathology, as well as recurrence rate.
A total of 23 patients, 14 males and 9 females, met the inclusion criteria. Table 1 presents demographics and study variables for the sample. On initial incisional biopsy, 4 (17.4%) cases showed a “cystic” mention in the pathology report, 18 cases (78.3%) exhibited solid ameloblastoma, and 1 (4.3%) showed peripheral ameloblastoma. Final pathology after definitive treatment showed solid/multi-cystic ameloblastoma in 20 (87%) cases, 2 (8.7%) were unicystic, and 1 (4.3%) was peripheral ameloblastoma. Overall, initial incisional biopsy and final pathology were concordant in 21 (91%) cases. After histologic investigation, the initial biopsy for 3 (13%) cases exhibited sampling error, which is defined as the sampled tissue not being representative of the entire lesion (Table 2).

Segmental resection was the definitive treatment in 14 (60.9%) cases while enucleation and curettage (E&C) were used on 6 (26.1%), and decompression followed by enucleation and curettage on 3 (13%) patients (Table 3). Postoperative follow-up from the day of definitive treatment ranged from 1 year to 15.6 years (mean 3.50 ± 3.22). Four patients (17.4%) had recurrent lesions, with 100% of them seen following conservative management (i.e., E&C or decompression with E&C). The time of recurrence after treatment ranged from 6 months to 10.75 years (mean 4.62 ± 4.25), with 1 case having more than 1 recurrence.

Incisional biopsies are acceptably reliable when combined with clinical exam of the lesion and radiographic presentation to select definitive surgical treatment for ameloblastoma. The chance of sampling error should be included in the informed consent with a low threshold for second incisional biopsy when clinical/radiographic findings are not consistent with histopathological report. Consult with an oral and maxillofacial pathologist is essential, both at initial and final histopathology evaluation. Future development of less-invasive treatments that combine medical and/or surgical management, given the benign nature of ameloblastoma, will help patients achieve cure in the long term.

1. Chen S, Forman M, Sadow PM, August M: The diagnostic accuracy of incisional biopsy in the oral cavity. Journal of Oral and Maxillofacial Surgery 74(5):959-964, 2016
2. Chouinard, AF, Peacock ZS, Faquin WC, Kaban LB: Unicystic ameloblastoma revisited: comparison of Massachusetts General Hospital outcomes with original Robinson and Martinez report. Journal of Oral and Maxillofacial Surgery 75(11):2369-2378, 2017