Pregnancy-like change of the breast. An ultrastructural study.

Foci of columnar, vacuolated epithelial cells similar to those of lactating breast are occasionally present in breast biopsies from nonpregnant and nonlactating women. A 27-year-old woman had this focal pregnancy-like change in an area of mild sclerosing adenosis. Ultrastructurally, the cells have some features that are similar to the secretory cells of normal lactation. Nevertheless, the cytoplasmic disorganization, mitochondrial shrinkage, and cellular exfoliation suggest that pregnancy-like change represents a combination of both secretory and involutional alterations.