Pathogenetic role of the stromal cells in endometriosis and adenomyosis

Ten cases of endometriosis of bowel, ovaries, uterine serosa and 10 cases of adenomyosis were studied. Blocks of tissue with areas of interest were submitted for serial sectioning of the entire block. Some sections were immunostained for oestrogen receptor, vimentin, Ber-EP-4 and cytokeratins. The common finding was the presence of type 1 nodules, consisting of isolated nodules of endometrial stromal cells without endometrial glands, along blood or lymphatic vessels. The stromal cells showed positive immunoreactivities for oestrogen receptor and vimentin, and negative reactivities for cytokeratins. Due to the absence of connection with adjacent endometriosis or adenomyosis, it is likely that these endometrial stromal nodules arise from the multipotential pericytes. In addition, in serosa of all cases of endometriosis, type 2 nodules, having adjacent mesothelium (Ber-EP4-) changing into epithelium (Ber-EP4+) and type 3 nodules, with non-endometrial epithelium (oestrogen receptor-) changing into endometrial gland (oestrogen receptor+) were identified. We believe that the formation of type 1 nodules from the pericytes and the transformation of the mesothelium into endometrial glands in type 2 and 3 nodules are accomplished through the process of induction by the endometrial stroma, and the proliferation is controlled by genetic, hormonal and immunological factors. Type 1, 2 and 3 nodules are likely to represent a histological continuum in the development of early endometriosis. Subsequent to the formation of endometriosis in the serosa, the pathway of development of endometriosis and adenomyosis is similar. Through the processes of induction and proliferation there is an increase in size of the stroma of type 1 nodules and that of endometrial tissue with subsequent fusion of the stroma of type 1 nodules and that of foci of adenomyosis or endometriosis. Consequently, there is enlargement of the stroma of the foci of adenomyosis or endometriosis. The 'newly enlarged stroma' serves as 'new soil' for further growth of the endometrial glands in the endometrial tissue.