Background: Mucoepidermoid carcinoma starts in the salivary glands and accounts for 5%–10% of all salivary gland tumours. Its intraosseous occurrence is rare and only accounts for 2%–3% of all mucoepidermoid carcinomas. This neoplasm often follows a long and indolent course. Also, given its ambiguous presentation and similarities to other dental pathologies, it often has a late diagnosis. In this instance, we present the case of a patient with an asymptomatic mandibular lesion, who underwent mandibular resection and reconstruction with fibula free flap.

Case report: A 32-year-old male patient reported discomfort when chewing, which was attributable to a self-detected mass localised in proximity to teeth 47 and 48. The lesion presented as a slight swelling without clear expression in the oral cavity mucosa. The rest of the physical examination revealed no abnormalities. Both the panoramic radiograph and computed tomography of the maxillary bones revealed lytic lesions in proximity to teeth 47 and 48, close to the mandibular angle. An incisional biopsy was performed, for which the pathological anatomy showed low-grade mucoepidermoid carcinoma. A resection was then performed, which involved a right hemimandibulectomy with ipsilateral cervical lymphadenectomy. The reconstruction was performed with a right fibula-free flap. Upon histological evaluation of the surgical specimen, an intermediate-grade mucoepidermoid carcinoma was found. The patient presented good post-operative evolution. Following a multidisciplinary assessment, the use of adjuvant radiation therapy was deemed necessary. The patient currently presents good evolution and has regular check-ups.

Conclusion: Intraosseous mucoepidermoid carcinoma is a rare salivary gland tumour. Given its low frequency, there are no studies that accurately describe its biological behaviour and prognosis.