Thyroid swellings with retrosternal extension are usually diagnosed by the history, clinical examination, and imaging. An intrathoracic mass extending into the neck can easily be mistaken for a thyroid swelling with retrosternal extension. A high degree of suspicion is necessary to identify such swellings that are confusing in their presentation. Here we report a case of mediastinal mass masquerading as a goitre with retrosternal extension along with spontaneous chylothorax, and was diagnosed to have non-Hodgkin's lymphoma (NHL). She was administered chemotherapy after the diagnosis.