Cystadenocarcinoma is defined as a malignant salivary gland tumor lacking features of other specific types of salivary gland tumors. It is histologically characterized by cystic and papillary growth. Cystadenocarcinoma was classified as a malignant cystadenoma in the 2005 WHO classification.
We report a case of synchronous double cancer involving cystadenocarcinoma in the left mandibular molar region and papillary thyroid carcinoma．
A 82-year old man visited our hospital because of pain in the left lower jaw. Clinical examination showed a soft elastic tumor in the left mandibular molar region. An incisional biopsy yielded a pathological diagnosis of cystadenocarcinoma. In addition, papillary thyroid carcinoma was found on the preoperative PET-CT examination.
Marginal resection of the mandible was performed under general anesthesia. The papillary thyroid carcinoma was treated by TSH suppressive therapy with thyroid hormone （Levothyroxine）.
There was no evidence of recurrence for us to 6 months after the operation, but unfortunately the patient died of another disease in the 7th month.
