Clear cell odontogenic carcinoma of the mandible: a treatment strategy

Abstract Clear cell odontogenic carcinoma (CCOC) is a rare odontogenic tumor of the jaws, histologically characterized by the presence of agglomerates of cells with eosinophilic cytoplasm. The patient, a 62-year-old Caucasian woman, presented an intraosseous lesion in the mandibular symphysis. A clinical examination revealed a discrete volumetric increase with a hard consistency, palpable to extraoral and intraoral examinations. Imaging studies revealed an extensive radiolucent area, without defined limits, extending from the region of the right second premolar to the left canine. Incisional biopsy analysis indicated a diagnosis of CCOC. The treatment proposed was segmental resection of the mandible with a safety margin. After six months without recurrence, definitive mandibular reconstruction was performed using an iliac crest graft, followed by rehabilitation with implant-supported denture after five months. After three years of post-resection follow-up, the patient has shown no evidence of recurrence or metastasis. She continues to be under follow-up. To conclude, CCOC must be considered a malignant tumor with aggressive behavior. Previous studies have shown that resection with free margins is a treatment with a lower rate of recurrence. Nevertheless, long-term follow-up is necessary for such patients.

This study documents a case of extensive CCOC of the mandible, treated with segmental resection of the mandible, with subsequent reconstruction using an autogenous iliac crest bone graft and rehabilitation with an implant-supported denture.

Case report
The patient, a 62-year-old Caucasian woman, visited our Oral and Maxillofacial Traumatology and Surgical service because of the chance discovery of an intraosseous lesion in the mandibular symphysis.  The panoramic radiograph showed an extensive radiolucent area, measuring approximately 5 mm along its longest axis, without defined limits, and extending from the region of the right second premolar to the left canine ( Figure 1A). Cone beam computed tomography revealed an extensive hypoattenuating area, with changes in the mandibular outline, as well as an area with perforated external cortical bone at  After six months of radiographic follow-up, the patient showed no signs of recurrence; hence, definitive mandibular reconstruction was performed using an autogenous iliac crest bone graft ( Figure 1B). This was followed by rehabilitation with an implant-supported denture after five months (Figures 1C and 2D). After three years of post-resection follow-up, the patient showed no evidence of recurrence or metastasis, continuing to be under follow-up by the team.

Discussion
Considered more aggressive than ameloblastoma, CCOC occurs more commonly in middle-aged women 14 .
This particular case occurred in the anterior region of the mandibular bone, which, based on recent literature, is considered rare 14 ; CCOC has no established pattern of occurrence, since a few years ago the predominant area was the anterior mandibular region 18 .
CCOC has no specific clinical and radiographic signs, making it difficult to diagnose. The most frequent symptoms include pain or discomfort, broadening of the mandible, mobility or displacement of teeth, and cortical destruction 5,9,13,14,19 . In this case, the patient showed no painful symptoms, which probably indicated in mandibular lesions, even in the absence of lymphadenopathies on initial clinical examination 7,9,20 .
The same observation has been made in the literature with regard to the indication for radiotherapy 21 .
Unfortunately, the number of patients receiving radiotherapy has been insufficient to evaluate the benefits of these treatment modalities.
An initial presentation of metastatic lymph nodules is rare. Some authors have indicated adjuvant ganglion removal therapy 8 and/or radiotherapy when there is evidence of extensive soft-tissue invasion, perineural invasion, or positive lymph nodes, or when removal of the tumor with free margins is not feasible 2, 3,9,12,17 .
In this case, partial surgical resection of the mandible was performed with margins of healthy bone tissue. In the absence of palpable lymph nodes and metastatic lesions, ganglion removal was not performed. Radiotherapy and chemotherapy were also not indicated. The patient has been radiographically followed up for three years, without signs of recurrence or metastatic lesions. In the literature, the general rate of recurrence has been reported as 41.8% and 86.7% among patients treated with curettage, and 29.8% among those treated with resection 21 . Among the patients with recurrence, 17% had distant metastases.
The time interval of disease recurrence ranged from 6 to 24 months for curettage, and 11 to 71 months for resection alone 9 .

Conclusion
In conclusion, CCOC must be considered a malignant tumor with an aggressive behavior. Previous studies have suggested that resection with free margins is a treatment associated with a lower rate of recurrence.
However, curettage or enucleation appears inadequate.
Moreover, long-term follow-up is necessary for such patients.

Conflicts of interest
None.