Primary Thyroid lymphoma is an uncommon malignancy, which can rarely cause severe dyspnea. Its commonly difficultly diagnosed and rapid diagnosis and management may be lifesaving. Here we report a case presented with sudden thyroid growth and severe dyspnea, who was diagnosed as primary thyroid lymphoma. A 70-year-old woman applied with fatigue, rapidly enlarged goitre and severe progressive dyspnea. She had severe hypoxemia with an artery oxygen saturation of 59.2% and arterial PO2 of 33.9 mmHg. The ultrasound of the neck showed an enlarged thyroid gland with a mass in the left lobe. After admission to the hospital her dyspnea worsened and oxygen and bronchodilator treatment gave no benefit. IV methylprednisolone was administered, and the patient’s symptoms partially improved. Meanwhile in spite of supportive therapy, the patient underwent urgent surgery for acute airway obstruction and thyroidectomy was performed. After surgery the diagnosis was high grade diffuse large B-cell non-Hodgkin’s lymphoma.