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.

畸胎瘤是起源于至少两个胚层的良性生殖细胞肿瘤，主要来源于外胚层和中胚层。成熟畸胎瘤是最常见的亚型，由分化良好的生殖细胞发育而来。虽然婴儿和幼儿的位置在性腺外，但成人的性腺受累。中线缺陷可以通过产前影像学诊断。在本病例报告中，介绍了一名患有成熟囊性畸胎瘤和产前腰椎中线闭合缺陷的新生儿。围产期初步诊断为脑膜脊髓膨出。然而，出生后在腰部肉眼观察到一个含有约5×5×3厘米大小的外生实体瘤组织的囊状囊，该肿瘤被完全切除。肿瘤切除后，在手术野底部观察到脊柱裂aperta和椎骨外生骨组织与椎间盘纵裂相容并完全切除。在短期的随访中，没有出现额外的问题。组织病理学诊断为“成熟囊性畸胎瘤”。总之，伴随纵裂的性腺外畸胎瘤很容易被误认为是脑膜膨出或其他常见畸形。应使用放射诊断方法提供围产期诊断，手术全切除和准确的病理诊断对于避免复发风险至关重要。伴随纵裂的性腺外畸胎瘤很容易被误认为是脑膜膨出或其他常见畸形。应使用放射诊断方法提供围产期诊断，手术全切除和准确的病理诊断对于避免复发风险至关重要。伴随纵裂的性腺外畸胎瘤很容易被误认为是脑膜膨出或其他常见畸形。应使用放射诊断方法提供围产期诊断，手术全切除和准确的病理诊断对于避免复发风险至关重要。