Definition of the microvascular pattern of the normal human adult mammary gland.

The present report provides a detailed description of microvascularization in the normal human mammary gland, and defines two novel morphometric parameters to be used as a reference when angiogenesis in breast carcinoma is evaluated. Microvascularization was analysed by histology, immunohistochemistry and computer-assisted analysis in a set of breast tissue samples taken from nine women, during the pre-ovulatory phase of the menstrual cycle. The two parameters designed for image analysis were: vascular density (VD): [microvessel number/(microvessel area + residual stromal area)] x 10 000; and vascular area ratio (VAR): [microvessel area/(microvessel area + residual stromal area)]. In the lobules VD (mean value +/- SE 2.48 +/- 0.14) and VAR (0.33 +/- 0.02) showed little variability and correlated significantly (P < 0.05). The areas occupied by microvessels, stroma and acini remained constant in all lobules (21.53 +/- 1.87%, 42.65 +/- 1.35% and 35.14 +/- 1.57%, respectively). Microvascularization of the lobules was of a sinusoidal type, with large S-shaped capillaries. In the ducts VD (2.95 +/- 0.16) and VAR (0.29 +/- 0.03) showed little variability but did not correlate significantly. Microvascularization of the ducts was of a classic type, with capillaries normal in size and shape. The expression of oestrogen (ER) and progesterone (PR) receptors was analysed by immunohistochemistry and compared with the morphometric results. ER expression levels were in the range 20-25% (24.3 +/- 2.1) and 14-18% (15.4 +/- 1.5) in lobules and ducts, respectively. PR expression levels were in the range 10-13% (11.1 +/- 1.6) and 14-17% (15.2 +/- 1.4), respectively. No correlation was found between ER/PR expression and vascularization parameters.