Midline hamartomas masquerading as meningomyeloceles or teratomas in the newborn infant

Congenital midline dorsal malformations in infants most commonly represent spina bifida cystica or teratoma. The five patients reported here are a distinct clinicopathologic entity. They presented at birth with a dorsal midline mass, with no neurologic impairment, and no hydrocephalus developed subsquently. The lesions were removed in all infants without significant morbidity. The masses were comprised prinicpally of mesodermal elements, i.e., bone, cartilage, fat, muscle, and fibrous tissue. The welldifferentiated cellular components, forming mature structures and the lack of primitive organoid structures as well as the absence of neoplastic characteristics, favors a diagnosis of hamartoma rather than of teratoma.