Large Hydatid Cyst of the Cervical Soft Tissue Extending to the Mediastinum: A Report of a Rare Case and Literature Review.

Hydatid disease (Echinococcus infection) is a parasitic condition primarily affecting the liver and lungs. Cervical involvement is extremely rare and can mimic other benign cystic neck lesions, making diagnosis challenging. We report a 35-year-old woman with a gradually enlarging left cervical mass extending toward the superior mediastinum, causing dysphagia and mild shortness of breath. Imaging revealed a large cystic lesion with daughter cysts abutting cervical vessels and the subclavian artery, with no abdominal or pulmonary involvement. The patient underwent transcervical excision with careful preservation of surrounding structures, followed by postoperative albendazole therapy. She recovered uneventfully and remains recurrence-free. This case highlights that hydatid disease should be considered in the differential diagnosis of cystic neck masses, particularly in rural or endemic regions. Accurate preoperative imaging is essential to delineate lesion extent, especially with mediastinal extension, and meticulous surgical excision without rupture is critical to prevent complications and recurrence.