This study was undertaken to test the hypotheses that, due to gradual accumulation of dead erythrocytes and their ingested products resulting from repeated
hemorrhage, older
endometriomas (whitish in color) contain chocolate fluid with higher
iron content than younger (brownish/blackish in color) ones with concomitant higher
collagen content and more adhesions. We recruited 30 premenopausal women with histologically confirmed ovarian
endometriomas and collected samples of their endometriotic lesions and chocolate fluid and measured the viscosity, density, and the concentration of total
bilirubin,
ferritin, and free
iron of the chocolate fluid. We also evaluated the lesion color and adhesion scores. In addition, we performed Masson trichrome and Picro-Sirius red staining on all endometriotic
cysts and evaluated the extent of
fibrosis in the lesions. We found that fluids taken from white-colored
endometriomas had significantly higher concentration of total
bilirubin,
ferritin, and free
iron, respectively, than black/brown-colored ones. In addition, older
cysts had fluids that had significantly higher density and viscosity. Fluid density correlated positively with the concentrations of total
bilirubin,
ferritin, and free
iron. Older lesions had significantly more
collagen content and higher adhesion scores. Taken together, these data supports the notion that older
cysts, having experienced more
bleeding episodes, contain chocolate fluid that is higher in viscosity, density, and
iron content and higher fibrotic content than younger ones. This provides another piece of evidence that endometriotic lesions are
wounds that undergo
repeated injury and repair, resulting ultimately fibrotic lesions that are resistant to hormonal treatment.