Figure 4.

Morphological and histological characteristics of mammary transplants carried in nulliparous hosts. (A) Whole mount of mammary outgrowths. (a) An outgrowth (generation III) of wild-type mouse. (b–d) Serial outgrowths (generations I–III, respectively) of PR-B transgenics. (B) Histology of mammary transplants of PR-B transgenics. (a) A small cluster of three acini adjacent to a collecting duct. (b) A branching duct structure with short ductules terminating in blind alveolar sacs (magnification, ×240).