Chondroid nodule in the female peritoneum arises from normal tissue and not from teratoma or conception product.

The pathogenesis of benign-looking cartilaginous tissue within the peritoneum is unknown. Chondroid metaplasia of subcoelomic mesenchyme has been suggested, as has been the case for other gynecological diseases such as endometriosis, peritoneal leiomyomatosis, or gliomatosis peritonei, but has never been proven. Chondroid nodules in the peritoneum may represent either teratomatous tissue, fetal rests from a conception product, or metaplasia of pluripotent mesenchymal cells. Herein, the unique genetic characteristics of ovarian teratomas (homozygous at many polymorphic microsatellite loci) versus normal tissues (heterozygous at the same loci) were used to investigate the origin of chondroid nodules in the peritoneum. DNA samples extracted from paraffin-embedded normal peritoneal tissue and chondroid peritoneal nodules from two patients were studied. In both cases, chondroid and normal tissue showed heterozygosity at each informative microsatellite locus on different chromosomes, with a profile similar to the mother. These results indicate that peritoneal chondroid nodules arise within the peritoneum, presumably from pluripotent mesodermal stem cells, and are not related to teratomatous proliferation, or previous pregnancy. This finding shows once again the plasticity and metaplastic potential of stem cells within the peritoneal cavity.