Stages do not describe pain, they describe how far endometrial tissue has spread throughout peritoneal cavity
STAGE IS NOT REFLECTIVE OF PAIN
Stage 1 (minimal): typically small patches, surface lesions
Stage 2 (mild): more extensive, but still very limited infiltration of tissue into pelvic organs, attaches to other areas
Stage 3 (moderate): more widespread, start to infiltrate pelvic organs, peritoneum, and other structures
Stage 4 (severe): infiltrative and affecting many pelvic organs and ovaries