Incidence and risk factors for recurrence, metastasis, and malignant transformation of ameloblastoma

The aims of the study were: to estimate the risk of recurrence of ameloblastoma and the factors associated with this risk; to determine the factors that should suggest ameloblastic carcinoma (AC) at diagnosis; and to estimate the rate of metastases or malignant transformation, as well as their risk factors. Records for all patients from our centre followed with ameloblastoma between January 2007 and May 2024 were exhaustively retrieved. Cox survival analysis for an ameloblastoma recurrence was then performed, and logistic models to study the risk of AC at the time of diagnosis and occurrence of metastases or of transformation into AC. A total of 175 patients with histologically proven benign ameloblastoma were included. In multivariate analyses, a radical surgical treatment appeared to be a strong protective factor against recurrence (hazard ratio (HR) 0.048 (0.006-0.365), P = 0.003). The metastases rate and transformation rate into AC at 5 years were 1% (0-2%) and 3% (0-7%), respectively. A histologically confirmed extraosseous extension of the initial ameloblastoma should be considered at risk of metastases or AC during the follow-up (HR 3.939 (1.089-25.06), P = 0.043). Closer follow-up is recommended, including thoracic imaging, in cases of ameloblastoma with extraosseous extension on histological sections.