Fig. 3. Histology of mammary tumor in Smad4^Co/CoWAP-Cre mice. (A,B) Normal (A) and hyperplasia (B) area of a L10 gland from a 6-month old mouse. (C) A mammary tumor mass at early stages showing undifferentiated alveolar structures. (D) In situ lesions from a 12-month-old mouse. The arrow indicates the center of initiating abscess. (E-G) Squamous cell carcinoma (E,F) and an abscess (G), showing cancer-pearl-like keratinization and onion-skin-like structures. Notice the increasing sizes of abscesses (arrows). (The boxed areas in C and E were further analyzed in Fig. 6C-F,G-J using molecular markers.) (H,I) The mutant mice also developed other types of tumors at much lower frequencies, such as carcinosarcoma (H) and adenocarcinoma (I). Scale bars: 120 µm in A,C; 240 µm in B,F,G; 136 µm in D; 90 µm in E; 80 µm in H; 60 µm in I.