Figure 2. Histopathology, cell proliferation, and apoptosis of mammary glands in TβRII-DNR+/+ mice. A. Normal mammary glands in a wild-type mouse (85 weeks of age). B. Lobular hyperplasia of the mammary glands in a TβRII-DNR+/+ mouse (61 weeks of age). Note the dilatation of mammary ducts containing eosinophilic secretion. C. Dysplastic hyperplasia of the mammary glands in a TβRII-DNR+/+ mouse (71 weeks of age). D, E. β-Casein strongly expressed in the lumen of alveoli and ducts of the mammary glands of a TβRII-DNR mouse (E, 110 weeks of age), whereas a wild-type mouse shows only intracellular expression (D, 85 weeks of age). F-H. Although few PCNA-positive cells are visible in the mammary glands of a wild-type mouse (F, 57 weeks of age), many positive cells are seen in normal-appearing mammary glands (G, 70 weeks of age) and lobular hyperplasias (H, 71 weeks of age) of TβRII-DNR+/+ mice. I-K. Many TUNEL-positive cells are present in normal mammary glands of a wild-type mouse (I, 57 weeks of age). However, only a few cells are positive by TUNEL in normal-appearing mammary glands (J, 66 weeks of age) and mammary proliferative lesions in a TβRII-DNR+/+ mouse (K, 71 weeks of age). A-C: H&E stain; D, E: β-Casein immunohistochemistry; F-H: PCNA immunohistochemistry; I-K: TUNEL reaction. Scale bars: A-E, 100 μm; F-K, 50 μm.