Cannabinoids inhibit breast tumor growth in vivo and the number of tumors generated per animal. (A) Volume time-course (scale bar: 1 cm) of the first tumor appeared in each animal. (B) Representative images (H&E staining) of the histopathology of the MMTV-neu-derived mammary tumors. Scale bars (from left to right): 200 μm, 100 μm and 50 μm. (C) Percentage of animals with 1, 2, 3, 4 or more tumors at the end of the treatment (90 days) in each experimental group. (D) Total tumor burden (total tumor volume per animal) determined 90 days after cannabinoid or vehicle treatment. (E) Volume of the tumors appeared in second, third or subsequent positions, 40 days after their appearance. The small size of the cannabinoid-treated groups is due to the very few second or third tumors appeared early enough to last 40 days in the animals before the end of the treatment (90 days after the appearance of the first tumor).