Metastasising clear cell odontogenic carcinoma: a case report and review of the literature

Primary odontogenic carcinomas are rare and examples which have metastasised are even more uncommon. We describe the first reported case of a clear cell odontogenic carcinoma which metastasised to distant bones, namely the 5th lumbar vertebra and hip, 3 years after initial diagnosis. The initial incisional biopsy was thought to represent a calcifying epithelial odontogenic tumour, but in the subsequent resection the tumour showed a prominent clear cell component admixed with squamous cells showing peripheral palisading, widespread infiltration and necrosis indicating a malignant neoplasm. Radiologically guided biopsy revealed a metastatic lesion in L5 vertebrae and left hip, confirmed by immunohistochemistry. The metastatic lesion had similar appearances to the first biopsy, and diagnosis was confirmed by comparison of histological features, immunohistochemistry and exclusion of a second primary lesion by clinical examination and imaging. The diagnosis of clear cell odontogenic carcinoma is a difficult one to make. The behaviour of these tumours is unpredictable. This case confirms that clear cell odontogenic carcinomas have the potential for distant metastasis and require long-term follow up.