Effect of major versus minor mastectomy on host immunity in canine mammary cancer

Surgical procedures can affect host immunity proportionally to the extent of surgical trauma. In cancer cases, surgery-induced immunosuppression can potentially promote tumour metastasis. The aim of this study was to investigate, in bitches with malignant mammary tumours, whether major surgery (total unilateral mastectomy or bilateral regional mastectomy) has a more negative effect than minor surgery (unilateral regional mastectomy) on components of host immunity. Twenty bitches with mammary cancer of clinical stage II or III were allocated to group A (minor surgery) or group B (major surgery) of 10 animals each receiving the same anaesthetic protocol for mastectomy. Immune cell measurements in blood [number of leukocytes, neutrophils, lymphocytes and platelets, and relative percentages of T-lymphocytes (CD3⁺) and their CD4⁺, CD8⁺ and CD5^low+ subpopulations] were performed before anaesthesia (day 0) and on days 3 and 10 post-mastectomy. On day 3, leukocytes, neutrophils and platelets numbers were higher (p = 0.016, 0.032 and 0.017, respectively) in group B than in group A. For all 20 bitches, T-lymphocytes and the CD4⁺, CD5^low+ T-cells were significantly decreased on day 3, but no significant differences were noted between groups. Minor mastectomy seemed to preserve innate immunity better than major mastectomy, but cellular immunity was rather equally affected.