Primary Intraosseous Squamous Cell Carcinoma of the Mandible: Report of a Case and Review of the Recent Literature

Primary intraosseous squamous cell carcinoma was reported in a 76-year-old Japanese woman. The patient exhibited bone expansion of the premolar-molar region of the left mandible with unilocular radiolucency surrounded by indistinct margins. Biopsy revealed a cystic cavity lined by non-carcinomatous squamous epithelium focally exhibiting epithelial dysplasia and distinct basal cell palisading. However, the overlying oral mucosa was normal in appearance. Under the provisional diagnosis of carcinoma arising in odontogenic cyst, segmental resection of the mandible and supraomohyoid neck dissection was performed. The resected mandible had a unicystic lumen lined by papillary or verrucous proliferation characteristic of welldifferentiated squamous cell carcinoma. However, invasion of the malignant cells along the displaced inferior alveolar nerve was not seen. There was no trace of unicystic ameloblastoma. No lymph node metastasis was confirmed. From these clinical, radiographic and histological findings, the present carcinoma was strongly suspected to be derived from a pre-existing keratocystic odontogenic tumor.