Rapid Growing Myofibroma of the Gingiva: Report of a Case and Review of the Literature

Purpose: Myofibroma is a rare benign tumor of myofibroblasts that rarely exhibits rapid enlargement and is misinterpreted as a malignant lesion. The aim of this study was to investigate its growth potential and to evaluate the usefulness of preoperative immunohistochemical study for an accurate diagnosis. Materials and Methods: A case of rapidly growing myofibroma of the lower gingiva was analyzed using 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography fused with computed tomography (PET/CT) and immunohistochemical study of Ki-67 and p53. The English-language literature from 1981 to 2012 also was reviewed. Results: An 18F-FDG PET/CT image displayed a high accumulation (maximum standardized uptake value, 14.1) in the lesion. A biopsy specimen showed mitotic activity of spindle-shaped cells, but atypia was not present. The MIB-1 labeling index was 10%, and the p53 test result was negative. The preoperative diagnosis of benign tumor of smooth muscle origin was made from the histopathologic and immunohistochemical features. In a review of 94 cases, tumors involved the mandible (33%), gingiva (23%), tongue (15%), cheek or buccal mucosa (12%), palate (8%), lip (4%), and other areas (5%). Nine cases (9.6%) were described as rapidly enlarging, and 8 cases (8.5%) were suspected of malignancy at initial diagnosis. The preoperative biopsy with immunohistochemical study established an accurate diagnosis in 83% of myofibromas, and no recurrences were reported in these patients. Conclusions: Careful diagnosis is necessary because these lesions sometimes present clinical and radiologic features that resemble those of malignant tumors. Preoperative immunohistochemical analysis should be performed to avoid misdiagnosis or unnecessary aggressive therapy. (C) 2014 American Association of Oral and Maxillofacial Surgeons