Is mild endometriosis always a disease?

The easy access to the pelvis via laparoscopy has led to an appreciable increase in the diagnosis of endometriosis in women with infertility or chronic pelvic pain. This could suggest a rising incidence of the disease but is probably largely related to the recently acquired ability to demonstrate minimal and mild lesions. However, estimates of the distribution of endometriosis in the female population might be unreliable due to lack of control of the variables which influence diagnosis of the disease in the initial stages. Analysis of data from prospective studies on asymptomatic women undergoing tubal sterilization reveals a markedly higher than expected frequency of endometriosis. This raises doubts on the clinical significance of the minimal lesions that are often found. The concept that initial endometriosis should always be treated to avoid worsening of the condition seems to lack a convincing rational basis and is not supported by definitive scientific evidence. Minimal/mild endometriosis could represent a temporary phase in an on-going process that usually results in cytolysis of recently implanted endometrial cells, whereas in a few immunologically 'tolerant' subjects, nodular, cystic and infiltrating lesions develop, with eventual progression to moderate and severe stages.