Invasiveness of endometriotic cells in vitro

The pathogenesis of endometriosis is not known. The currently favoured theory is that viable endometrial cells, shed from the endometrium into the pelvic cavity by retrograde menstruation, reattach and invade other tissues. We used a collagen gel invasion assay to assess invasive potential of endometriotic cells. The invasion indices of cells from peritoneal endometriotic lesions and a metastatic bladder carcinoma cell line (EJ28) were similar (2·2-15·6 vs 8·4-11·6) whereas cells from normal endometrium and non-metastatic carcinoma cells (RT112) were non-invasive (indices <1). Invasiveness of endometriotic cells might contribute to the pathogenesis of endometriosis.