We report a case of intra-osseous carcinoma arising from a mandibular cyst. An 81-year-old woman visited our hospital because of a right mandibular swelling. Radiographic examination showed a multilocular radiolucent lesion and bone expansion, extending from the midline to the right mandibular angle. The clinical diagnosis was a mandibular cyst and marsupialization was performed. The histopathological specimen showed a cyst wall with an epithelial layer and connective tissue. After marsupialization, the swelling and the radiolucent area of the mandible decreased. However, about 7 months later, the mesial region of the lesion became swollen again, and it was biopsied. At that time, we obtained a pathological diagnosis of squamous cell carcinoma.
Marsupialization does not permit histopathological examination of all sites of the lesion. Therefore, when it is performed for large mandibular cysts such as in our case, we should consider the posibility of an intra-osseous carcinoma arising from the lesion.