Figure 1. Representative histopathological images of breast cancer metastases in lungs of mice injected with 4T1 cancer cells. Breast cancer metastasis was investigated by histological examination of the lungs isolated from mice during necropsy carried out in animals injected with saline (control) (A) or after 0 (B), 2 (C), 3 (D), 4 (E) and 5 (F) weeks from the injection of 4T1 cancer cells. Hematoxylin and eosin staining, magnification of 100X. Additional images under lower optical magnification (20x) present breast cancer metastasis in samples of lungs resected from mice at the second (G) and fifth (H) week of breast cancer development. Cancer metastases are marked with white arrows. More experimental details are given in the Materials and methods section.