Fig. 1.

Macrophages enter the ductal epithelial layer in early breast cancer lesions. H&E staining of mammary gland sections show progression from healthy mammary ducts in FVB wild-type glands (age 20wks; a) to early lesions classified as hyperplasia and mammary intra-epithelial neoplasia (age 22wks; b) to invasive tumors (age 26–30wks; c) in the MMTV-HER2 mouse model. Bars: 100 μm. Mammary glands from FVB wild-type (20wks; d) or pre-malignant MMTV-HER2 mice at age 14wks (e) and 22wks (f) were stained against F4/80 (macrophages) and CK8/18 (epithelial cells) and against F4/80 and smooth muscle actin (SMA) (g–i). Bars: 10 μm. The mean±SEM of the percentage of ducts containing IEM is shown; FVB: N = 4 mice, 14wks; N = 3 mice, 22wks; N = 5 mice (j). P values were calculated with 95% confidence by Mann–Whitney test