Recurrent Micropapillary Carcinoma with Lymph Node Metastasis in bitch: Unilateral Mastectomy and OncoMap-Guided Therapeutic Approach – Case Report

Mammary neoplasms are among the most common oncological disorders in small animals, with most cases being malignant and strongly influenced by hormonal factors, particularly estrogen and progesterone. Mastectomy remains the treatment of choice, with the surgical approach determined by the affected gland(s) and tumor size. Before surgery, the presence of metastases should be evaluated using imaging modalities such as abdominal ultrasonography, thoracic radiography, and/or computed tomography. Adjuvant therapies, including chemotherapy or targeted treatments, are indicated according to the histological type, tumor grade, clinical stage, and immunohistochemical profile. This report describes a case of micropapillary carcinoma with lymphatic metastasis in a female dog that developed tumor recurrence despite appropriate surgical management and adjuvant chemotherapy. Following recurrence, mastectomy of the remaining mammary chain was performed, and genomic analysis using OncoMap guided a change in therapeutic strategy, revealing the ineffectiveness of the previous protocol and resulting in a survival outcome that differed from reports in the literature. Keywords: Hormones. Mammary Neoplasm. Metastasis. Surgery.