Epidemiology and Risk Factor Analysis of Canine Mammary Gland Tumors Requiring Surgical Excision in South West Nigeria

Mammary gland tumors are the most common neoplasm in intact female dogs and represent a major surgical oncology challenge in small animal veterinary practice. This analytical epidemiological study investigates the prevalence, histopathological classification, and risk factors associated with canine mammary gland tumors requiring surgical excision at four veterinary facilities in Oyo, Lagos, and Ogun States, South West Nigeria, between January 2021 and December 2023. A case-control design compared 96 tumor-bearing dogs with 96 age-matched healthy female controls. Data collected included reproductive history, age at first estrus, dietary patterns, breed, parity, and body condition score. All excised tumors were submitted for histopathological grading. Malignant mammary tumors were diagnosed in 58% of surgically excised masses, with mixed mammary carcinoma being the predominant malignant type. Intact reproductive status was the strongest risk factor identified, with intact dogs having a 4.7-fold higher tumor risk relative to spayed controls. Dogs first spayed after two estrous cycles had an intermediate risk profile. Age above six years and obesity were significant additional risk factors. These analytical findings fill a critical epidemiological gap in Nigerian veterinary oncology literature and provide evidence for public health messaging targeting companion animal sterilization. Histopathological data from this study contribute to the growing understanding of mammary tumor biology in tropical canine populations. Keywords: canine mammary tumor, surgical oncology, risk factors, South West Nigeria, mastectomy.