It is important to suspect the possibility of an accessory parotid gland tumor firstly based on its anatomical position. A necessary condition for a tumor to be an accessory parotid gland tumor is for imaging examinations to show no continuity with the parotid gland tissue on CT and MRI. A confident diagnosis can be made if secretory ducts flowing into Stensen’s duct can be observed on images such as sialography, sialo-CT and MR- sialography. However, even if secretory ducts can not be observed, the possibility of a tumor derived from the accessory parotid gland cannot be completely ruled out. FNA is useful in observing salivary gland tissue and in qualitative diagnosis [6]; however, it is necessary to be aware that there are cases of false positives and false negatives. A definitive diagnosis should be made based on an isolated sample.

Diseases which should be differentially diagnosed from accessory parotid gland tumors are tumors developing in the cheek region, including benign tumors such as schwannoma, dermoid cyst, and lipoma; as well as lymph node and masseter muscle tumors, Stensen’s duct primary tumors, minor salivary gland derived tumors, and aberrant salivary gland tumors. The histological subtypes of these tumors can be differentiated based on histopathological findings; however, tissues from which the latter four types of tumors are derived can be identified by employing the following examinations.