Primary intraosseous carcinoma arising from an odontogenic cyst: A case report.

Cyst-like lesions in the mandible rarely develop into malignancies, and the reported incidence is between 0.3 and 2%. The present study describes a rare case of primary intraosseous squamous cell carcinoma of the mandible arising from an odontogenic cyst. A 59-year-old female was referred to Asahi University Murakami Memorial Hospital (Gifu, Japan), with acute pain in the right molars. An initial examination revealed buccal swelling and paresthesia of the mental nerve. Following an intraoral examination, the oral mucosa was confirmed to be normal, however, percussion pain was experienced between the lower right first premolar and second molar. Panoramic radiography revealed a retained lower right wisdom tooth and an irregular radiolucent area between the lower right molar and a mandibular angle with unclear margins. Computed tomography revealed diffuse bone resorption and an extensive loss of cortical bone on the buccal and lingual sides. A biopsy was performed and the pathological diagnosis was of a squamous cell carcinoma arising from the epithelial lining of the odontogenic cyst. Radical dissection was subsequently performed, however, histopathological examination of the resected specimen revealed neither invasion into the surrounding tissues penetrating the periosteum nor lymph node metastasis at the right submandibular lesion. Following the pathological diagnosis of primary intraosseous carcinoma (PIOC), the patient received 6,000 Gy radiation as post-operative radiotherapy and chemotherapy with oral administration of tegafur, gimeracil and oteracil potassium. The patient is currently undergoing follow-up examinations. Although PIOC arising from an odontogenic cyst is rare, it should be considered as a differential diagnosis for radiolucency of the jaw bone, particularly in older patients exhibiting a history of cystic lesions.