Cervical thoracic duct cyst: a differential diagnosis of left supraclavicular swelling.

We report a 79-year-old woman with a left sided neck mass that appeared to be a thoracic duct cyst (TDC). A TDC is a rare condition. Generally, it may cause local symptoms, but most likely it presents as an asymptomatic swelling. The pathogenesis of TDC is not known, but different theories on the development, including weakness of the duct wall and obstruction of the lymphoid flow, have been suggested. Sonography with needle aspiration, examination of the cyst fluid, and CT scan/MRI may raise the suspicion of the TDC diagnosis. Surgery with total excision of the cyst, followed by histopathological examination confirms the diagnosis.