RESUMO
Benign fibrous histiocytoma (BFH) is a common mesenchymal lesion on the skin where it is better known as dermatofibroma. It mainly affects areas of the integument exposed to the sun. It can occur in the mucous membranes, being quite unusual in the oral cavity. This article presents a rare case of benign oral fibrous histiocytoma in childhood. An eleven-year-old male patient sought the stomatology clinic of the dentistry course at a reference university in northeastern Brazil, complaining of an asymptomatic increase in volume on the cheek, with an evolution of approximately two years. On intraoral examination, a lesion in the cheek mucosa was observed, measuring approximately 4 cm. The lesion had a nodular, circumscribed, reddish appearance, showing ulcerated areas covered by a yellowish pseudomembrane on its surface. The clinical diagnostic hypothesis was pleomorphic adenoma. Excisional biopsy was performed and, after morphological and immunohistochemical evaluation, the diagnosis of BFH was reached. Although it is a lesion with an excellent prognosis, BFH must be carefully analyzed for the differential diagnosis with malignant neoplasms that may have a mild appearance, such as fibrosarcoma or dermatofibrosarcoma. In addition, other benign lesions such as desmoplastic fibroblastoma, myofibroma, myopericytoma and nodular fasciitis may, in some histological sections, mimic the microscopic appearance of benign fibrous histiocytoma. In this reported case, immunohistochemical evaluation was essential to conclude the diagnosis of BFH(AU)