Fig. 4

Histological types of mammary intraepithelial neoplasia (MIN). a–d This figure illustrates the three types of MIN lesions found in a 129:Stat1 ^−/− female, stained for Forkhead box A1 (a–c; 106-week-old nulliparous female) and CD3 (d; 90-week-old tumor-bearing female). a Ductal pattern with a branching duct filled with large oval pale (LOP) cells. Scale bar = 300 μm. b Cystic with expanded luminal cystic space lined by LOP cells. Note the lack of any appreciable host response in a and b. Scale bar = 300 μm. c Solid micronodular pattern with small nests of cells in dense connective tissue. Scale bar = 200 μm. d A higher-magnification image of a more advanced solid nodular MIN showing dilated vessels and dense round cell infiltrate with CD3⁺ T cells (see Fig. 9). Scale bar = 100 μm