Midline hamartomas masquerading as meningomyeloceles or teratomas in the newborn infant.

Congenital miline 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 subsequently. The lesions were removed in all infants without significant mobidity. The masses were comprised prinicipally of mesodermal elements, i.e., bone, cartilage, fat, muscle, and fibrous tissue. The well-differentiated 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.