Histological Features in the Mammary Glands of Female Dogs throughout Lactation

Abstract

The objective of this study was to describe the histology of the mammary glands of female dogs throughout lactation. Twelve lactating female dogs were operated 4, 7, 10, 14, 21, 28, 35, 42, 56, 70 and 84 days post-partum; four mammary glands of each animal were excised for histological, ultrastructural and morphometric examination. During early lactation and mid-lactation, all lobes and lobules within the same gland had similar features; alveoli were well developed and distended and had a spherical to slightly ovoid structure, with muscular fibres grasping them around; inflammatory cells were seen in the inter- and intra-alveolar space; mammary lobules were separated with a scant amount of connective tissue. In late lactation, connective tissue was abundant and dense, with large numbers of inflammatory cells; alveoli appeared to be irregularly shaped and collapsing, shrunken or fully collapsed. Number of alveoli per lobule and number of epithelial cells per alveolus, as well as diameter of alveoli and height of epithelial cells decreased as lactation progressed. The third mammary glands (from caudal to cranial) had a significantly smaller number of alveoli, but not of epithelial cells per alveolus, than each of the two mammary glands caudally to that. The results suggest that progressive involution of the normal mammary gland starts around the end of the 2nd month of lactation and continues until the end of the 3rd month.

Lactation‐related mammary gland pathologies—A neglected emergency in the bitch

“…Inflammatory cells are present in both the inter‐ and intra‐alveolar space of all mammary glands. Macrophages are the predominant (50%–65%) subpopulation, followed by lymphocytes (35%–50%) and neutrophils (<1%; Orfanou et al., 2010). The presence of inflammatory cells in the mammary tissue indicates that cellular defence has an important role in local inflammations.…”

“…The presence of inflammatory cells in the mammary tissue indicates that cellular defence has an important role in local inflammations. Increased intra‐alveolar presence of inflammatory cells in late lactation participates in the removal of lipocytes or protein micelles, which contributes to the physiological involution of the mammary gland (Orfanou et al., 2010).…”

Histologic Evidence of the "Sick Lobe" Carcinogenesis Theory and the Frequency of Intraepithelial Lesions in the Mammary Glands of Female Canines with no Clinical Signs of Neoplasia

“…In our case, the physiological stages of the canine estrus (reproductive cycle) such as proestrus, estrus, and diestrus, as proposed by Sorenmo, et al [9] were taken into account. However, Mouser, et al [17] used inclusion criteria of human breast pathologies and thus considered UDH when more than two cell layers were present; [38] according to those criteria, the primary criterion for classifying a lesion as UDH is several epithelial cell layers with regular proliferation within the duct lumen without any other sign of abnormal cell growth [9,[24][25][26]. Under our criteria, this would not be considered a pathologic change.…”

“…The animals were reproductively active (intact), had more than one estrus and had no evidence of clinical mammary disease. The physiologic status of the MG was morphologically determined according to the criteria defined by Rehm, et al [24] Orfanou, et al [25] and Santos, et al [26]. The approach was used because the densities of estrogen and progesterone receptors in the mammary epithelial cells vary among the stages of the estrus cycle, which influences the activity (growth or involution) of the gland.…”

Identification of regulatory networks and hub genes controlling mammary gland development and lactation in dairy goats during the late lactation, dry period, and late gestation stages

“…After a long period of lactation, mammary gland tissues begin to involute, and mammary gland cells undergo apoptosis. The number of mammary acinar and duct branches decreases [14]. Moreover, during the late lactation stage, the milk synthesis and secretion capacities and cell viability of epithelial cells signi cantly decline [15].…”