BRAF mutation in five cases of sinonasal ameloblastic tumors and their clinical course: a case report

Sinonasal ameloblastic tumors exhibit unique clinical, pathological, and genetic traits distinct from mandibular bone cases, accounting for the majority of ameloblastic tumors. Recent findings emphasize a notable genetic disparity, showing high BRAF mutation rates in mandibular cases versus very low rates in maxillary cases.

We analyzed five sinonasal ameloblastic tumor cases treated at Kyushu University Hospital. All patients were Japanese, four male and one female, and their age ranged from 43 to 73 years. Three were diagnosed with ameloblastoma, with one experiencing recurrence that progressed to a life-threatening condition owing to the lack of effective treatment. One patient was histologically diagnosed as ameloblastic carcinoma, and another patient, although histologically diagnosed as ameloblastoma, presented with lymph node metastasis, confirming it as a metastasizing ameloblastoma with clinical malignancy. Local radical resection was performed in all five patients; however, three of them had positive resection margins, and two received postoperative (chemotherapy) radiation therapy. Recurrence was confirmed in two patients, with one patient undergoing chemoradiation therapy and achieving local control. BRAF mutations were detected in only one patient.

Owing to anatomical challenges in achieving negative resection margins and the low BRAF mutation frequency, sinonasal ameloblastic tumors exhibit poor prognosis with high recurrence, malignancy, and metastasis rates. When factors predicting recurrence post-radical resection in these tumors are identified, chemoradiation therapy is recommended as an adjuvant postoperative treatment. However, it should be noted that this presentation of adjuvant therapy is based on the experience of only five cases.