A case of multiple bone metastases developing from clear cell odontogenic carcinoma of the mandible

Clear cell odontogenic carcinoma (CCOC) was reclassified from a benign tumor to a malignant tumor by the WHO classification in 2005 because of its aggressive nature and potential for local recurrence and distant metastases. Only 81 well-documented cases have been reported to date to the best of our knowledge. A patient was referred to our clinic because of rapid swelling of the left side of the mandible. Computed tomography (CT) showed a bone defect in the mandible, but no cervical lymph node metastasis. We suspected a malignant tumor and performed a biopsy. We diagnosed CCOC of the left side of the mandible and performed segmental mandibulotomy. Histopathologically, the tumor consisted of clear cells containing diastase-digestive PAS-positive granules. Furthermore, immunohistochemistry showed that the tumor cells were immunoreactive for cytokeratins (CKs) 7, 17, 19, Ki-67 and vimentin, but non-reactive for CK20, smooth muscle actin (SMA), epithelial membrane antigen (EMA) and S-100 protein. The Ki-67 labeling index (LI) was 10%. We finally diagnosed CCOC. One year 5 months after surgery, the patient died of multiple organ failure caused by the multiple bone metastases. We discuss this rare case of multiple bone metastases developing from CCOC of the mandible and review the literature.