First described by Hansen in 1985 [1], clear cell odontogenic carcinoma (CCOC) is a rare odontogenic tumor with approximately 100 cases reported so far [2], [3], [4], [5]. The incidence of this tumor peaks in the fifth to seventh decades (with a mean age of 56.5 years; range of 17–89) with a slight female preponderance (male to female ratio, 10:17). CCOC typically localizes in the anterior segments of the jaws and more affects the mandible rather than the maxilla. Clinically, patients usually present with a painless swelling of the jaw. In addition, tooth mobility and pain are occasional symptoms. Radiologically, the tumor presents an ill-defined radiolucency and tooth root resorption. Histologically, CCOC can be classified into biphasic, monophasic and ameloblastomatous patterns, amongst which biphasic is the most common pattern. This tumor is characterized by sheets and islands of vacuolated, glycogen-rich clear cells. In the biphasic pattern, nests of cells with clear cytoplasm mixed with cells containing eosinophilic cytoplasm are present. In the monophasic pattern, a high proportion of clear cells can be found. In the ameloblastomatous pattern, the tumor may present peripheral palisading [6], [7]. CCOC is locally aggressive and has the potential for lymphatic and hematogenous metastasis [8]. The recommended treatment is radical surgery because partial or incomplete resection may result in recurrence [9].

Here, we report a case of maxillary CCOC morphologically mimicking sclerosing odontogenic carcinoma (SOC), and harboring Ewing sarcoma RNA binding protein 1 (EWSR1) and activating transcription factor 1 (ATF1) gene fusion.