Tumor-like lesions of the secondary müllerian system. Immunohistochemical investigations and differential diagnosis.

Even postnatally, the female peritoneum (mesothelium and submesothelial mesenchyme) has a potential for differentiation (secondary Müllerian system) similar to that of the embryonic coelom epithelium. This potential is manifested in some cases under an evident hormonal stimulus, and in other cases without an apparent cause. The functional similarity of the differentiation products of the secondary Müllerian system with structures of the primary Müllerian system is underscored by their common antigens which have been detected immunohistologically, including the expression of steroid receptors. Of the lesions of the secondary Müllerian system, in particular endosalpingiosis is of special importance because of its frequency and the in some cases grave therapeutic consequences. Atypical distinguished even using immunohistological techniques.