Endometriosis Pathology

The gross appearance of endometriosis at operation is usually quite characteristic and, to an experienced surgeon, is sufficient for diagnosis. The smallest (and presumably earliest) implants are red, petechial lesions on the peritoneal surface. With further growth, menstrual-like detritus accumulates within the lesion, giving it a cystic, dark brown, dark blue, or black appearance. The surrounding peritoneal surface becomes thickened and scarred. These "powder burn" implants typically attain a size of 5-10 mm in diameter. With progression of disease, the number and size of lesions increase, and extensive adhesions may develop. When present on the ovary, cysts may enlarge to several centimeters in size and are called "endometriomas" or "chocolate cysts." Severe disease can erode into underlying tissues and distort the remaining organs with extensive adhesions. In addition to these traditional presentations, endometriosis lesions can have a variety of nonclassical appearances: clear vesicles, white or yellow spots or nodules, circular folds of peritoneum ("pockets"), and visually normal peritoneum (lesions so small they can only be detected microscopically).

The distribution of lesions also exhibits a characteristic pattern. Solitary lesions are possible, but multiple implantations are the rule. The most common site of disease is the ovary (approximately half of all cases), followed by the uterine cul-de-sac, uterosacral ligaments, the posterior surfaces of the uterus and broad ligament, and the remaining pelvic peritoneum.

Endometriosis