Implantation versus infiltration: The Sampson versus the endometriotic disease theory

It has been assumed that endometriosis is a progressive disease, with growt h and development of lesions being inevitable once the disease has started. The implantation and the metaplasia theories describe the mechanism of ini tiation of endometriotic lesions, but do not explain the different clinical manifestations of endometriosis. To explain the variable expression, growt h and development of lesions into severe disease, a new endometriotic disea se theory is proposed. This theory suggests that progression of endometrios is to endometriotic disease is considered similar to the onset and progress ion of a benign tumour. In this theory, the most important factor in the de velopment of endometriotic disease is not the initial implantation/metaplas ia, but cellular changes such as mutations. According to this theory, endom etriotic disease develops from endometriotic cells that have 'escaped' the influence of protective and regulatory factors in the peritoneal fluid.