A Large Substernal Goiter Mimicking Lung Mass

Substernal goiter, also known as a retrosternal goiter, is defined as a thyroid mass that exhibit 50% or more of its volume located below the thoracic inlet. This enlarged thyroid gland grows inferiorly and passes through the thoracic inlet into the thoracic cavity. Substernal goiters are most descended into the anterosuperior mediastinum and may also extend into the posterior mediastinum behind the trachea or even into the posterior thoracic cavity. The appearance of this substernal goiter on chest radiograph may show smooth soft tissue mass which characteristically displaces the trachea. Here, we describe a rare case of a large substernal goiter in 53-year-old lady, who denied any obstructive symptoms or any noticeable thyroid swelling in the neck region. Incidentally, large mass was discovered on her right lung on chest radiograph during screening and she was considered to have a lung cancer at the first sight. Tomographic examination revealed a large mediastinal mass extending from the inferior pole of right thyroid lobe, compressing the lateral wall of trachea on the right upper lung region. Considering the large appearance of intrathoracic mass without much mediastinal structure deviation on conventional radiograph raise suspicion of lung cancer, thus computed tomography plays an important role in determining the origin of the mass.