Immunohistochemical labeling of PRLR in canine mammary tissues. a) Non-neoplastic mammary tissue. Signal can be detected in epithelial cell cytoplasm and in alveolar secrete. Connective tissue cells are mostly negative. b) Non-neoplastic mammary tissue. Epithelial cells are flattened and exhibit a strong signal. c) Mammary adenoma. The adjacent non-neoplastic tissue shows more intense positive staining than the neoplastic one. This tissue is from an original block used for the study. d) Mammary adenoma. Signal is present in epithelial cells. e) Mammary adenoma. Staining is mainly localized to the basal epithelial cell layer. f) Mammary adenocarcinoma. Signal is present in epithelial cells and rarely in some fibrous tissue cells. g) Mammary adenocarcinoma. An intense signal is present in epithelial cells. h) Mammary adenocarcinoma. Only a weak signal signal is present in epithelial cells. Immunoperoxidase staining, anti-human PRLR antibody.