[A Case of Ectopic Mediastinal Goiter Developed during Administration of Rheumatrex].

We report a case of ectopic goiter that developed during administration of rheumatrex and in which we had difficulty in differentiating it. A 46-year-old woman had been diagnosed with rheumatoid arthritis(RA) and had been taking rheumatrex(12.5 mg/week)for the past 2 years. When she visited a local doctor, she was diagnosed with a thyroid tumor and was referred to our hospital. A plain chest X-ray showed compression of the trachea. A neck ultrasound showed an 8 cm tumor extending from the lower pole of the left thyroid lobe into the mediastinum. A contrast-enhanced CT scan showed tracheal deviation and an 8 cm tumor extending from the left thyroid lobe toward the mediastinum. Fine-needle aspiration biopsy was performed on the tumors in both thyroid lobes, but the diagnosis was benign. Surgery was performed to relieve the pressure on the trachea. A left lobectomy and removal of the left cervical tumor were performed. Histopathological diagnosis was adenomatous goiter in both cases. There was no continuity between the left thyroid lobe and the left anterior cervical tumor, so the tumor was diagnosed as ectopic goiter.