A Rapidly Growing Swelling in the Posterior Mandible: Clear Cell Odontogenic Carcinoma

Abstract

Clear cell odontogenic carcinoma (CCOC) is an extremely rare odontogenic malignancy with an infiltrative and destructive growth pattern. They represent the lesions of the lower end of the spectrum of malignancy having 10–20% chance of metastasis. In 1992, World Health Organization (WHO) classified this as a locally aggressive benign tumour. However, in 2005, WHO renamed it as CCOC due to its aggressive behaviour. Histologically, this tumour shows prominent islands of clear cells with well-defined outline. In the head and neck region, clear cells are found in many different tumours such as salivary, odontogenic or tumours of metastatic in origin. Apart from histological characteristics, molecular analysis plays a crucial role. About 83% of CCOCs express EWSR1-ATF1 rearrangement. However, this rearrangement was identified in several other tumours, and it is difficult to differentiate CCOC from hyalinizing clear cell carcinoma (HCCC) of salivary origin. They both occur in maxillofacial region and can be differentiated by imaging and demonstrating mucin in HCCC. Wide local excision is the treatment of choice with long-term follow-up. Neck dissection and adjuvant radiation therapy may be considered in some cases.