Unicystic Ameloblastoma Revisited: Comparison of Massachusetts General Hospital Outcomes With Original Robinson and Martinez Report

Robinson and Martinez established unicystic ameloblastoma (UA) as a distinct pathologic entity in 1977. Using their original description, the aims of this study were to compare the clinical presentation and outcomes of UA treated at Massachusetts General Hospital (MGH) with outcomes reported in the original article. This was a retrospective cohort study of MGH patients treated for UA during a 15-year period. Patients were included if they had a confirmed clinical and histologic diagnosis of UA. The primary predictor variable was the source of the study sample (MGH vs Robinson and Martinez). Secondary variables included age, gender, radiographic appearance, treatment, and histologic subtype. The primary outcome variable was the number of recurrences over time comparing the 2 groups. There were 19 patients (10 female and 9 male patients) in the MGH group and 20 patients (10 female and 10 male patients) in the Robinson and Martinez study. The lesions were predominantly unilocular (13 in MGH group and 19 in Robinson and Martinez group), located in the mandible (18 in MGH group and 20 in Robinson and Martinez group), and tooth associated (12 in MGH group and 14 in Robinson and Martinez group). No statistically significant demographic differences were noted between the 2 groups. In the MGH group, 13 cases (68%) exhibited mural or intramural ameloblastic epithelium, 4 (21%) were luminal or intraluminal, and 2 were unknown. However, histologic configuration was not reported in the Robinson and Martinez group. MGH patients were treated by enucleation (n = 7, 37%) or resection (n = 12, 63%) compared with enucleation in 100% cases in the Robinson and Martinez group. Overall, the disease-free survival rate was higher in the Robinson and Martinez group, but the difference was not statistically significant (P = .089). Within the MGH group, 100% of recurrences occurred in patients with mural invasion treated by enucleation. The results of this study support UA as a distinct entity based on demographic, clinical, and radiographic criteria. Outcomes in the MGH group were influenced by the degree of ameloblastic epithelial invasion and suggest that this variable should be considered when planning treatment.