Canine and Feline Melanoma: Diagnosis, Treatment, and Prognosis

Melanocytic tumors are clinically important in veterinary oncology because their biological behavior, diagnosis, and prognosis vary substantially by species and anatomical site. Canine oral melanoma is characterized by aggressive local invasion and early metastatic spread, whereas melanocytic tumors at other canine sites and in cats show distinct clinicopathologic features that require different diagnostic and therapeutic approaches. This narrative review was based on a structured literature search of PubMed, with searches organized around epidemiology and biological behavior, diagnosis, treatment, and prognosis. A total of 1887 records were identified after removal of duplicates, and 111 publications were ultimately included following title, abstract, and full-text screening. This review summarizes current evidence on the epidemiology, molecular biology, diagnosis, clinical staging, treatment, and prognosis of canine and feline melanocytic neoplasms. Diagnostic approaches include cytology, histopathology, immunohistochemistry for amelanotic tumors, advanced imaging, sentinel lymph node mapping, and emerging molecular methods. Therapeutic options include surgery, radiation therapy, electrochemotherapy, chemotherapy, therapeutic vaccination, immune checkpoint inhibitors, and targeted therapies. Prognostic factors include tumor location and stage, histologic grade, mitotic count, nuclear atypia, pigmentation, tissue invasion, and molecular biomarkers. Surgical excision remains the cornerstone of treatment for localized disease, but effective systemic therapies for advanced melanoma remain limited. Ongoing molecular characterization, genomic profiling, and comparative oncology research may improve prognostic stratification and support more precise therapeutic strategies.