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Origin of teratomas

The histologic, cytologic, and clinical features of teratomas are discussed in relation to the possible methods of origin of these unusual lesions. It is suggested that there are two groups of teratomas. One type seen in the gonads and possibly in the posterior abdominal wall is derived from germ cells by a process of parthenogenesis. The second type seen in the sacrococcygeal region, the head, and the chest is related to sequestration of cells of the blastula before differential blocking of the genome has occurred, and may be regarded as a derivative of an incomplete conjoined twin.