Developmental stages of embryo-like bodies in teratoma testis.

Small bodies, comparable in their morphology with that of the early developmental stages of mammalian embryos, are observed uncommonly in certain testicular teratomata (Melicow, 1940; Dixon and Moore, 1953; Evans, 1956); and although an enormous number of these embryolike structures may be scattered haphazardly throughout a teratomatous growth, it is only rarely that such bodies (Figs. 2, 5) mimic closely the form of normal early human embryos (Fig. 1). In the case to be described numerous embryoid bodies were present in many areas of a testicular teratoma and many of these bore a remarkable resemblance to normal early primate embryos. The mimicry was so extraordinary that it was considered worth while studying a few of these embryo-like structures in detail in serial sections so that their anatomy could be compared with that of normal presomite mammalian embryos of corresponding morphological stages of development. An attempt was made also to trace the various ontogenetic phases in the hope of gathering some information relevant to the evolution and ultimate fate of these structures.