Dermoid or epidermoid cysts usually appear as a midline swelling in the sublingual region or the floor of the mouth. There have been several case reports of lateral neck epidermoid cysts, which are considered to arise as median cysts and extend to the space between the mylohyoid and hyoglossus muscles. We report a rare case of epidermoid cyst arising between the submandibular gland and the platysma. A 40-year-old woman was referred to our hospital for evaluation of an asymptomatic swelling in the submandibular region. The MR imaging showed a well-defined cystic mass between the submandibular gland and the platysma. The lesion was extirpated under general anesthesia. No adhesion to the surrounding tissues was observed. White caseous material was contained in the lesion. Histopathologically, the cyst lumen was filled with keratin and lined by stratified squamous epithelium. There was no skin appendage, and a final diagnosis of epidermoid cyst was made. The postoperative course has been good, without any complications.
