• endometriosis;
  • growing teratoma syndrome;
  • histogenesis;
  • mature teratoma;
  • ovary;
  • secondary neoplasm

Development of secondary neoplasm in mature teratomas is a long-term potential risk in growing teratoma syndrome (GTS) of the ovary. The origin or histogenesis of the secondary neoplasm, however, is scarcely understood. We herein report two cases of GTS that began secondary neoplastic change 10 and 22 years after initial presentation. In one case, microscopic carcinoids were scattered over various mature elements derived from three germ cell layers: some were close to the intestinal-type glands or adipose tissue and others lay in the glia. This implies that these carcinoids multicentrically originated from pluripotent stem cells that had been latent in various mature tissues. In contrast, the other case had only one focus of intestinal-type tubular adenocarcinoma, measuring 5 mm in diameter, adjacent to the intestinal-type glands. Malignant transformation of intestinal-type glands is most likely to account for this adenocarcinoma. In both cases, peritoneal mature teratomas also contained foci of endometriosis, almost exclusively in their glial components. In conclusion, the present cases suggest two diverse histogenesis of secondary neoplasm in GTS and a specific role of glia in the development of endometriosis in peritoneal teratomas.