[Semb's proliferating centers in the breast]

In 17% out of 671 cases of proliferative mastopathy, peculiar symmetrical complexes of pathological structures, proliferative centers (PC) were found. As they enlarged, their spherical shape changed and the structure became nonhomogeneous. In the epithelium of different PC both in their enlargement and from the periphery to the center the nucleus-cytoplasm index decreased, its variation coefficient increased. This is considered to be the evidence that PC are the early stage of dysplasia of the mammary gland when the stage of proliferation is overcome by the stage of structure formation. The symmetrical pattern of PC may be explained only by its derivation from the primary spherical group of cells, the "marginal" state of the tissue apparently common for dysplasia and carcinoma of the mammary gland.