Immunohistochemistry of differentiation markers in human breast explants. (A-B) Immunohistochemistry of K-14 before organ culture. Note that the myoepithelial cells of the normal tissue have heavy brown cytoplasmic stain (A). In tumoral tissue the K-14 positive cells are scattered throughout the acinus (B), thus, it does not label anymore myoepithelial cells. (C, E, G) – Expression of K-14, CK8&18 and SMA respectively in non-cultured human breast tissues. (D, F, H) – Expression of K-14, CK8&18 and SMA in breast explants cultured with 10 nM E2 for 21 days. (Scale bar, 100 μm).