Myofibromas and myofibromatosis of the oral region: A clinicopathologic analysis of 79 cases

The clinicopathologic features of 79 myofibromas or myofibromatoses of the oral and maxillofacial region were studied. The case studies were taken from the files of the Armed Forces Institute of Pathology. The tumors affected 44 males and 33 females (gender was unknown in 2 cases). The patients' ages at diagnosis ranged from birth to 84 years, with mean and median ages of 26.6 and 22 years, respectively. Four patients had infantile myofibromatosis; 2 had extraoral bone lesions and 2 had multiple subcutaneous tumors. In descending order, tumors involved the mandible, tongue, lips, cheek or buccal area, maxilla or palate, pterygomandibular raphae, floor of mouth, and submandibular gland. One third of the tumors affected the bones of the jaws; 12 were central and 15 were cortical or periosteal. All medullary tumors occurred in patients under age 18. On gross examination, the lesions were firm, homogenous or whorled, white-grey fibrous masses that ranged in size from 0.5 to 5.0 cm. Microscopically, all tumors demonstrated a pattern of nodules or bundles of spindle cells separated by areas of greater cellularity and crescent-shaped vascular spaces. Distinct hemangiopericytoma-like areas were present in 22 cases. Despite apparent circumscription, the tumors commonly infiltrated and entrapped adjacent muscle, nerve, or salivary tissue, Immunohistochemically, 37 of 37 and 39 of 39 tumors stained positively for α-smooth muscle actin and muscle-specific actin, respectively, with the former eliciting a more intense reaction. Eight of 8 tumors were weakly positive for CD68, and one case stained focally with S-100 protein. No desmin staining was present in 36 tumors examined. Diagnostic interpretations by the pathologists seeking consultation were malignant or aggressive tumors in 31 cases and other benign conditions in 26. Nine were interpreted as myofibromatosis and 13 offered no interpretation. Thirty-two patients were alive and free of tumor an average of 42 months after initial diagnosis. Four patients had one recurrence each, and 2 had lesions recur twice. Myofibromas are relatively common soft tissue tumors of the maxillofacial region, which have been misinterpreted as malignant or aggressive lesions.