We have previously reported that epithelial cells appear to be clustered in the perilobular stroma of the human lactating breast', that phenomenone has not beendocumented well in the literature. The present study is aimed at to clarify the nature and characteristics of the clustered-epithelial cells in relation to basement membrane, epithelial cell death and myoepithelial cells.
We studied the mammary gland of Wister female rats in various stages of resting, pregnant and lactating phase histochemically and electron microscopically. Basement membrane was detected by immunohistochemically (indirect peroxidase method) on 4% paraformaldehyde (PFA)-fixed frozen section using anti type rv collagen (goat, Southern Biotechnology Assoc. Inc. Birmingham, AL, USA) and electron microscopcally. Apoptotic cell death was shown by in situend labeling method on formalin-fixed paraffin-embedded section. The myoepithelial cells were observed by alkaline phophatase Azo dye method on frozen section, and by immunohistochemical staining for actin (smooth muscle) (clone; 1A4, Sigma Chemical Co. St Louis, MO, USA).