Teratoma in human tail lipoma.

We report a case of a rare congenital teratoma that developed in a lipoma attached to a remnant human tail. A male newborn baby presented with a large, 3-cm mass with an open margin, which pedunculated from a tail attached to the midline skin of the coccygeal area. Magnetic resonance images demonstrated multiple sacral spinal bifida without cord tethering, and also showed neural roots and a lipoma and teratoma with peripheral homogeneous high density and internal low density on T(2)-weighted images. Intraoperatively, we found and dissected two nerve roots from the filum terminale which extended into the mass. Pathologic examination of the mass revealed abnormal differentiation of respiratory epithelium and squamous cell metaplasia along the open margin of the mass, and mainly lipoma in the rest of the mass. We suggest that this case could support the hypothesis of transient teratomatous cells in the pathogenesis of the spina bifida with lumbosacral lipoma.