Figure 2

Morphological and immunohistochemical analysis of MMTV(LA)-induced HIT and LM3 mammary tumors growing in vivo. (a, b) Hematoxylin/eosin-stained tumors. (a) Moderately differentiated hormone-independent tumors (HIT). Papillary formations into lumen of cystic ducts and less differentiated zones with small glandular structures. Original magnification ×100; inset ×400. (b) LM3 poorly differentiated adenocarcinoma with abundant infiltrated vascular stroma. Areas with sarcomatous appearance and apoptotic images (black arrowheads). Original magnification in (a, b) ×100; inset ×400. (c-f) Leukemia inhibitory factor (LIF) immunohistochemistry. (c) HIT: heterogenous and regular distribution mainly in poorly differentiated areas with cytoplasmic and nucleic positive staining; intense cytoplasmic staining increasing peripherally indicates a secretory pattern (arrowhead). (d) LM3 tumor: patchy LIF staining. Inset: positive cytoplasmic staining; the ill-defined cell membrane pattern with granular cytoplasmic staining indicates LIF secretion (arrowhead). (e) Involuting (48-hour) and (f) lactating mammary glands were used as positive and negative controls, respectively, for LIF staining. Original magnification in (c-f) 250×; inset: 400× (g, h) Stat3 (signal transduction and activators of transcription 3) immunohistochemistry. (g) HIT: stromal and predominantly epithelial positive nuclear staining in solid areas. Inset: stained nuclei were also seen in glandular regions. (h) LM3 tumor: intense cytoplasmic positive staining in stromal and epithelial cells. The inset shows a negative gland surrounded by positive stromal cells. Original magnification in (g, h) 250×; inset: 400×