A Rare Case of Adult Cervicothoracic Cystic Lymphangioma Presenting as Neurogenic Thoracic Outlet Syndrome.

Cystic lymphangioma (CL) is an uncommon congenital malformation of the lymphatic system, often occurring in the head, neck, or mediastinum, potentially causing compression symptoms like dysphagia or dyspnea, and in rare cases, neurogenic thoracic outlet syndrome (nTOS). This report details a case of a 38-year-old male with a four-year history of a left lower neck mass, experiencing tingling in his left forearm over the last six months. The examination revealed a left supraclavicular cystic mass, with imaging suggesting CL compressing neurovascular structures. The patient underwent successful complete surgical excision through a left supraclavicular approach. Histopathology confirmed CL, with no recurrence observed over 19 months. The case highlights that cervicothoracic CL with adult presentation can cause pressure symptoms including nTOS. It also underscores the role of a multimodal diagnostic approach to differentiate it from other neck masses and that a supraclavicular approach can effectively remove the cyst, especially when the lower extension is not deep and there is no surrounding inflammation, thereby leading to relieving pressure and preventing recurrence.