Primary Central Intraosseous Mucoepidermoid Carcinoma of the Mandible.

Mucoepidermoid carcinoma (MEC) is the most common malignant tumor of the salivary glands. Rarely, MEC may arise primarily within the jaw bones as central intraosseous MEC, whose pathogenesis remains uncertain but may involve malignant transformation of ectopic salivary gland or odontogenic cystic lining. A 31-year-old male presented with an asymptomatic, slowly enlarging mass in the left mandible that had been growing for over a decade. Initial radiographs revealed a multilocular radiolucent lesion, and the patient postponed treatment until progressive growth caused functional impairment. Clinical examination revealed a firm extraoral swelling and a fluid-filled multinodular intraoral lesion extending across the left mandibular body, with tooth mobility. Computed tomography showed an expansive multilocular osteolytic lesion involving the mandibular body, angle, and ramus. An incisional biopsy confirmed low-grade central intraosseous MEC, characterized by mucous, intermediate, and epidermoid/squamoid cells with mucin production demonstrated by alcian blue and periodic acid-Schiff (PAS) staining. The patient underwent composite hemimandibulectomy with 2.0 cm margins and remains free of disease after two years of follow-up. This case highlights the indolent yet locally aggressive nature of central intraosseous MEC and underscores the importance of early diagnosis and appropriate surgical management for a favorable prognosis.