Ameloblastoma: 25 Year Experience at a Single Institution

Abstract

Ameloblastoma is a rare, locally aggressive odontogenic neoplasm, accounting for fewer than 1 % of head and neck tumors. Recent literature suggests that the initial surgical approach and histologic growth patterns are the most important prognostic determinants in ameloblastoma. The aim of this study was to compare the clinical presentation, management, and outcomes of patients with ameloblastoma with data reported in the literature; the study spanned 2 decades at a single institution. The institution's database was searched for all patients with pathologically confirmed ameloblastoma, diagnosed between 1990 and 2015. The data collected included sex, age, clinical and imaging findings, management, histologic pattern, clearance of surgical margins, length of follow-up, time to recurrence, and disease-related mortality. The potential risk factors of recurrence were evaluated using log-rank test, proportional hazard model, and Fisher exact test. Review of the database yielded 54 patients with pathologically confirmed ameloblastoma and follow-up. Recurrence was noted in 13 (24 %) patients. Surgical approach was associated with the risk of recurrence (6.1 % following radical resection vs. 52 % following limited surgery, p = 0.002). There were trends toward higher recurrence rate in the group with pathologically documented positive margins (p = 0.054) and in follicular ameloblastoma (p = 0.35). Transformation into ameloblastic carcinoma was identified in two patients. There was no disease-related mortality. Our study confirms the recent data regarding the importance of radical surgical resection in management of ameloblastoma. Surgical approach appears to be the strongest predictor of tumor clearance.

Keywords: Ameloblastoma; Ameloblastoma histologic pattern; Ameloblastoma management; Ameloblastoma pathology; Ameloblastoma prognosis; Ameloblastoma recurrence.

Fig. 1

Kaplan–Meier curves demonstrating time to first recurrence in 54 patients by gender (a), location (b), initial surgical approach (c), and microscopic involvement of margins (d)

Fig. 2

Histologic patterns in solid/multicystic ameloblastoma. a Plexiform ameloblastoma demonstrates interweaving fascicles of neoplastic cells with hyperchromatic columnar nuclei, polarized away from the basement membrane (“reversed polarity”, “piano-key” arrangement). b Islands of granular ameloblastoma demonstrate central stellate reticulum-like cells with abundant eosinophilic granular cytoplasm. c Acanthomatous ameloblastoma shows squamous-type differentiation of the central stellate reticulum-like cells, while maintaining the reverse polarization of the nuclei in columnar cells lining the nests. d Desmoplastic ameloblastoma shows islands of odontogenic epithelium in abundant desmoplastic stroma. e Follicular ameloblastoma islands demonstrate peripheral columnar cells exhibiting reversal of polarity and central stellate-reticulum like cells with cystic degeneration. f Basal cell type ameloblastoma islands contain basaloid cells with scant cytoplasm and peripheral palisading, reminiscent of basal cell carcinoma. [H&E stain; original magnification ×25 (a, b, d, e, f); original magnification ×50 (c)]

Fig. 3

Histopathology of the tumors in 2 patients with secondary ameloblastic carcinoma. a Patient 1. Initial specimen demonstrates benign-appearing nests of basal cell type ameloblastoma. b Recurrent tumor 6 years later shows dedifferentiation into ameloblastic carcinoma. c Patient 2. Nests of follicular ameloblastoma (top) transition into a sheet-like proliferation of pleomorphic, mitotically active cells of ameloblastic carcinoma (bottom). d Corresponding ki-67 immunostain highlights the low proliferative activity in ameloblastoma component and high proliferative activity in the emergent ameloblastic carcinoma. [H&E stain (a–c); antibody, ki-67 (d); original magnification ×25]