Superior vena cava syndrome secondary to thyroid cancer.

It is uncommon for thyroid cancer to present with superior vena cava syndrome. Obstruction of superior vena cava can develop as a result of intrinsic and extrinsic spread of the thyroid cancer. The usual presentation of this disease entity is a neck mass with symptoms and signs suggestive of superior vena cava obstruction. Superior vena cava obstruction is commonly caused by lung cancer and lymphoma. However, thyroid cancer can cause superior vena cava obstruction by downward tumour spread into the mediastinum causing extrinsic compression, which will lead to narrowing and thrombosis of the major venous system in the chest. Paraganglioma can also present with superior vena cava obstruction and it mimics thyroid cancer microscopically. Proper staining should be performed to differentiate between the two diseases. This could be the first case of this kind reported in the literature.