Giant dermoid cyst of the neck can mimic a cystic hygroma: using MRI to differentiate cystic neck lesions

OBJECTIVE: To describe differential features of giant cervical dermoid cysts and other cystic lesions of the head and neck. METHODS: Case report including magnetic resonance imaging, surgical excision, pathologic examination and correlation. RESULTS: We report the case of a 15-year-old boy who presented for evaluation of a slowly enlarging doughy submental mass. Ultrasound showed some features consistent with a cystic hygroma and both sclerotherapy and surgical excision were discussed with the family. However, an unusual solid component on magnetic resonance imaging (MRI) mitigated toward surgical excision. At surgery, the cystic mass was excised and measured 9.5 cm x 5.5 cm x 4.0cm. Histology showed a giant dermoid cyst similar to those seen in the ovary. The solid component was a smooth spherical collection of inspissated sebum. CONCLUSIONS: The unique MRI characteristics of giant dermoid cysts can help to separate these rare lesions from more common cystic hygromas. Fine needle aspiration should be considered for questionable lesions before treatment with OK 432 or similar agents.