Endometriosis is characterised by angiogenesis.

Different tissues were stained by immunohistochemistry for CD31 (endothelial cell marker) and the pericyte marker aSMA (present in mature vessels only). Representative images are shown. A. In the uterus (eutopic endometrium), most CD31 positive blood vessels are also aSMA positive, indicated by the black arrow-heads in the enlargements. ‘e’ = endometrium; ‘m’ = aSMA positive myometrial cells; ‘v’ = large-mature blood vessels present in the myometrial layer. B. Abdominal wall consisting in large part of striated muscular tissue (mu), with some connective (c) and fat (f) tissues. A surgically induced endometriotic lesion is present on the left image, and visible as aSMA positive myometrial tissue (at the bottom-left of the low-magnification image; blue arrow-head). C & D. Intraperitoneal (C) and subcutaneous (D) lesions. In the endometrial layer of the lesions (e), most blood vessels are DC31 only positive (red arrow-heads in the enlargements); ‘m’ = myometrium (aSMA positive cells).