Fig. 2. Mammary tumor mass formation in Smad4^Co/CoWAP-Cre and Smad4^Co/CoMMTV-Cre mice. (A) Morphologically denser areas detected in the fourth mammary gland of a P16.5 Smad4^Co/CoWAP-Cre mouse. This female is 6 months of age and went through more than four pregnancies. (B) An enlarged view of the boxed area shown in A. Arrowhead and arrow indicate areas with different morphology, respectively. (C) Multiple tumor masses (arrows) in a third gland of a one-year-old Smad4^Co/CoWAP-Cre mouse. (D,E) An 8-month-old Smad4^Co/CoWAP-Cre mouse developed multiple mammary abscesses, two of which are indicated by an arrow and an arrowhead. The area indicated by the arrowhead is shown in E. (F) A curve showing percent of mammary mass Smad4^Co/CoWAP-Cre (n=36), Smad4^Co/CoMMTV-Cre (n=34) and control mice. The controls include Smad4^Co/+WAP-Cre, WAP-Cre and Smad4^Co/Co mice. About 50 controls younger than 1 year and 20 between 1 and 1.5 years of age were followed and none developed mammary tumor and/or abscess. Scale bar: 3.5 mm in A; 0.87 mm in B,C.