Examples of MDA-MB-231 tumors and tumor histology from 5αP- and 3αHP-treated mice. (A) Large aggressive tumor from a 5αP-treated mouse, with histologic sections showing (B) invasion of rib-cage muscle by the spreading tumor cells, and (C) higher magnification of region with numerous mitoses (arrows). (D) Residual tumor from a 3αHP-treated mouse, with no signs of invasion (E) and showing region of tumor with numerous apoptotic and necrotic cells (F). Formalin-fixed sections (5 μm) stained with hematoxylin and eosin. Scale bars at 1.0 cm for whole tumors (A, D), at 160 µm for (B) and (E), and at 40 µm for (C) and (F).