Multiple keratocystic odontogenic tumors associated with nevoid basal cell carcinoma syndrome having distinct PTCH1 mutations: a case report

Nevoid basal cell carcinoma syndrome (NBCCS) is a rare autosomal dominant disorder characterized by developmental abnormalities and a predisposition to cancers. Although multiple jaw tumors, such as keratocystic odontogenic tumors (KCOTs), are one of the most frequent complications in NBCCS, the molecular mechanism for how KCOTs develop in NBCCS is poorly understood. A 15-year-old girl with 2 jaw tumors was diagnosed as NBCCS according to the clinical criteria. The pathologic findings indicated that the 2 tumors were consistent with KCOTs. A PTCH1 mutation, c.1472delT, was detected in her peripheral blood as well as in the 2 tumors. Interestingly, an additional PTCH1 mutation, c.264_265insAATA, that was not present in the peripheral blood, was found in the maxillary tumor but not the mandibular tumor. The Ki-67 labeling index was significantly higher in the maxillary KCOT (17.7%) than in the mandibular KCOT (14.3%). These findings indicate distinct molecular mechanisms of tumorigenesis in these KCOTs.