Mature cystic teratoma mimicking meningomyelocele.

Teratomas are benign germ cell tumors originating from at least two germ layers, mostly of ectodermal and mesodermal origin. Mature teratomas are the most common subtype and develop from well-differentiated germ cells. Although the location is extragonadal in infants and young children, gonadal involvement occurs in adults. Midline defects can be diagnosed on prenatal imaging. In this case report, a newborn with mature cystic teratoma and a prenatal lumbar midline closure defect was presented. The perinatal preliminary diagnosis was meningomyelocele. However, a cystic sac containing exophytic solid tumoral tissues approximately 5 × 5 × 3 cm in size was seen macroscopically in the lumbar region after the birth, and this tumor was totally resected. After tumor excision, spina bifida aperta and vertebral exophytic bony tissue compatible with diastematomyelia were observed at the bottom of the surgical field and were totally resected. In the short-term follow-up, no additional problem occurred. The histopathological diagnosis was "mature cystic teratoma." In conclusion, extragonadal teratoma accompanying diastematomyelia could easily be mistaken for meningomyelocele or other common malformations. Perinatal diagnosis should be provided using radiodiagnostic methods, and total surgical excision and accurate pathological diagnosis are essential to avoid the risk of recurrence.