The radicular cyst is the most common odontogenic cyst and is caused by inflammation. It can become atypically large, although the size of the radiographic osteolysis says nothing about the entity of the lesion. This case shows an unusually large multilocular radicular cyst expanding buccally from tooth 46 in a patient with severe autism who can only be treated under general anesthesia. The clinical and radiological picture as well as the intraoperative situation was more indicative of an aggressive cyst or benign tumor. The lesion was surgically completely removed and the teeth 46, 47 and 48 were extracted because of poor compliance and prognosis. Histopathology revealed a radicular cyst. There were no postoperative complications. After eight months, the lesions had almost completely reossified.

One of the most frequent pathologies of jaw bone is a bacteria-induced inflammation at the apices of teeth with subsequent bone resorption that typically presents as a radiolucency in radiographs. Usually, corresponding clinical and radiographic findings correlate and allow for an accurate diagnosis. However, occasionally an unexpected and completely different diagnosis presents as documented in this case report. In a 55-year-old female patient, a radicular cyst was suspected in her right maxillary bone. The treatment plan included a cystectomy as well as apical surgery of the adjacent and root-canal filled teeth 15 and 16. However, the intraoperative finding absolutely did not fit a radicular cyst but rather a mucous retention cyst, as could be confirmed subsequently by histopathology. The diagnosis of a mucous retention cyst within the jaw bone is extraordinary and as such has never been described before in the literature.