Fig. 1.

Differences in the microanatomy of human vs. mouse breast. a Normal human breast section. The solid pink background highlights the dense stroma with mature collagen surrounding ducts and lobules (Hematoxylin-eosin (H&E) stain of formalin-fixed paraffin-embedded (FFPE), 40×). b Normal mouse breast lacks the dense stromal background. Most of the tissue is composed of adipose cells (H&E stain of FFPE, 40×). c The arrow points to the interface between the outer dense collagenous inter-lobular stroma and the inner intra-lobular specialized stroma in human breast (H&E stain of FFPE, 400×). d Normal mouse breast ducts are directly surrounded by the adipose tissue, without a stromal interface. Also note that there is not a well-formed lobular structure with branching TDLU as seen in the human lobule in panel C (H&E stain of FFPE, 400×)