Synovial cysts of the temporomandibular joint are rare. They commonly occur in the wrist, knee and feet. The main symptoms of synovial cysts occurring in the temporomandibular joint include preauricular pain and swelling, and surgical removal is the gold-standard treatment. A 54-year-old woman who presented with swelling of the right temporomandibular joint visited Kyungpook National University Dental Hospital. She had undergone enhanced computed tomography from another hospital, which showed a 1.1 × 0.8 × 1 cm well-defined rounded cystic lesion on the lateral area of the right temporomandibular joint. A synovial or ganglion cyst was suspected. The cystic lesion was surgically removed under general anesthesia and was histopathologically diagnosed as a synovial cyst. Histopathological findings show a lumen surrounded by loose fibrous tissue, and the lining is in a folded form and is composed of synovial cells.

Dentigerous cyst is considered one of the representative cystic lesions, which accounts for approximately 15%-30% of the odontogenic cysts. Although its recurrence rate is low, a small proportion of dentigerous cysts converted into ameloblastomas, squamous cell carcinomas, and mucoepidermoid carcinomas. Here we present an uncommon case characterized by histopathological transformation from a dentigerous cyst to an ameloblastoma, and further investigate the factors contributing to its conversion.

Ameloblastoma is a benign odontogenic tumour of epithelial origin and comprises 1% of maxillomandibular tumors or cysts. The incidence of pathological changes such as ameloblastoma from the follicle of impacted third molar was reported to have low incidence. However, there are many reports that asymptomatic third molars are related with various pathological conditions. A case of ameloblastoma secondary to third molar extraction and subsequent sagittal split ramus osteotomy (SSRO) had not been reported. At the right ramus area, radiolucent lesion had been noted at 6 years after the surgical extraction of the third molar followed by SSRO for the mandibular prognathism. The lesion was proved to be the basal cell type ameloblastoma. There had been no significant bony lesion before or 1 year after the SSRO. The tumour was successfully removed and there was no evident recurrence at 4 year of the follow up after the removal of the ameloblastoma. There are some reports suggesting the pathologic potential of the pericoronal tissues of impacted third molars to develop odontogenic keratocysts and ameloblastomas. The current case reports a rare possibility of ameloblastic change at the site of uneventful healing after third molar extraction and orthognathic surgery.

Canalicular adenoma is an uncommon, benign salivary gland tumor. It has a significant predilection for occurrence in the minor salivary glands, with most cases occurring in the upper lip, followed by the buccal mucosa and palate. Rarely, canalicular adenoma can involve the major salivary glands, such as the parotid gland. Only a small number of cases of canalicular adenoma of the parotid gland have been reported in the literature. We report a rare case of canalicular adenoma on the left parotid gland of an 81-year-old man, and present a review of the literature.

Carcinoma ex pleomorphic adenoma (Ca ex PA) is an uncommon malignant tumor. It is an aggressive salivary carcinoma, arising from a primary or recurrent benign pleomorphic adenoma (PA). The most common clinical presentation of Ca ex PA is a firm mass in the parotid gland. Here we report a case of Ca ex PA, arising from a recurrent benign PA in the right parotid gland, in a 70-year old female patient. The lesion was first diagnosed as a PA and a superficial parotidectomy was performed. Re-operation was performed for recurrent PA. The second recurrence was diagnosed as Ca ex PA.