Melanoma of the dog and cat: consensus and guidelines
Melanoma in dogs and cats presents a significant challenge to veterinarians worldwide. Although our understanding of these tumors is advancing, uncertainties and controversies persist. Oncologists created a comprehensive guideline document that integrates current knowledge and provides expert clinical guidance on managing melanoma in these animals and this is the summary:
Incidence and Prevalence:
Dogs: Melanocytic tumors are common, with malignant melanoma accounting for 70% of these tumors and 7% of all malignant tumors. They are more frequent in middle-aged to older dogs and certain breeds, such as Scottish Terriers and Golden Retrievers. The most common sites are oral (62%), cutaneous (27%), digital (6%), and subungual (4%).
Cats: Melanocytic tumors are rare, comprising less than 1% of all cancer diagnoses. They most commonly occur in the eye, haired skin, and oral cavity.
Clinical Signs and Diagnosis:
Oral Melanoma in Dogs: Usually found in the gingiva, lips, tongue, and hard palate. Signs include bad breath, drooling, bleeding, difficulty eating, and weight loss. Diagnosis involves physical examination, cytology, and biopsy.
Cutaneous Melanoma in Dogs: Appears as pigmented masses on the skin, which can be benign or malignant. Diagnosis includes visual inspection, cytology, and histopathology.
Subungual Melanoma in Dogs: Presents as a swollen, painful toe with lameness or excessive licking. Diagnosis involves physical examination and biopsy.
Ocular Melanoma: Signs vary based on the affected structure and may include a visible mass, eye discharge, and vision changes. Diagnosis requires a thorough eye examination and histopathology.
Treatment:
Surgical Resection: Wide-margin surgical removal is the primary treatment for melanoma in all locations.
Radiotherapy: Essential for managing canine oral melanomas, used both as primary and adjuvant therapy.
Adjuvant Therapies: Immunotherapy or chemotherapy may be offered to dogs at high risk of metastasis.
Prognosis and Referral:
Prognosis: Depends significantly on the tumor's location, size, and stage. Oral melanomas tend to have a poorer prognosis compared to cutaneous melanomas, which are often cured with wide surgical excision.
Referral: Referral to a specialist may be considered based on the clinician's experience, the complexity of the case, and access to advanced diagnostic and therapeutic options. Recording tumor size before excision and staging through imaging and lymph node assessment are crucial steps before referral.
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