Skin-covered lesions in the sacrococcygeal region include an unusual array of congenital tumors and malformations. Excluding the easily recognized meningomyelocele, there are over 50 other conditions that occur, many of which seem to be important in linking the disciplines of teratology and oncology. While it is impossible to precisely determine the manner in which these arise, there is suggestive evidence that early structures incorporated within the caudal cell mass of the embryonic tail may play an important role. The present paper reviews the basis for this speculation from both the literature and a series of 136 cases.