A newborn male infant with a fist-sized anterior neck mass bulging to the right side, was admitted to our hospital soon after birth. He was spontaneously delivered after 35 weeks of gestation with a birth weight of 2,650g. There was no evidence of hydroairnios. Because the baby presentad with severe respiratory distress and marked cyanosis, intratracheal intubation was performed at once, and mechanical ventilation was started. Roentgenography showed a cervical mass of soft tissue nature without calcification, which caused no tracheal deviation. A thyroid scintigram demonstrated marked swelling of the right lobe of the thyroid gland including a cold area in it, suggesting a diagnosis of thyroid neoplasma. Laboratory data were within normal limits, and α-fetoprotein was normal under 1,000 ng/ml. CT scanning revealed several intracranial low density areas that seemed to have caused the respiratory distress. The mass was nodulated, partly solid and firm, partly cystic to palpation, and increased gradually in size. Operation was performed on the 23rd day after birth, and the mass was located in the right lobe and isthmus of the thyroid gland, and was easily enucleated. The patient's recovery was uneventful. Microscopic examination revealed multiple types of tissue representing the three germinal layers, including squarnous epithelium, glial tissue, bone and columnar epithelium. He has grown normally now, one year after operation. Twenty one cases of teratoma including ours were reviewed from the Japaneses literature.
