We encountered a case of mediastinal teratoma which was enlarged to the anterior region of the neck. The patient was a 16-year-old female. She came to the hospital with complaints of anterior neck swelling, odynophagia, and dysphagia. CT scan and MRI were examined and showed a mass occupying the area of the low neck to the upper anterior mediastinum. One month after first examination, the anterior neck tumor was not palpable. It had been spontaneously absorbed. An operation revealed the mediastinal tumor which was 10×6×4.5cm in the diameter. The histopathological diagnosis indicated a mature teratoma comprised of three germlayers and thymic tissue. No malignant elements were present.
