Malignant melanoma is one of the most common canine oral tumors. However, other locations, including the digits, eyelids, skin, etc. may be affected. Dogs of all breeds and sizes can be affected, but those with heavily pigmented oral mucosa, such as Chows, may be at an increased risk for developing melanoma. The most common sites of metastasis are regional lymph nodes (60-80%) and lungs (50-60%), and metastasis at the time of diagnosis is associated with a poorer overall prognosis. Occasionally, metastasis can occur at distant sites (lungs, liver) without evidence of spread to the regional lymph nodes (termed "skip metastasis). Recommended staging includes blood work, three-view thoracic radiographs, abdominal ultrasound, and aspirates of both mandibular nodes regardless of lymph node size. Additional imaging with high-detail dental radiographs or advanced imaging (CT-scan) may be warranted and will aid in surgical planning as well as evaluation of other regional lymph nodes (e.g. retropharyngeal). Surgical removal is the primary method of treatment for local control. Aggressive surgery is associated with a better prognosis than conservative surgery, and lymph nodes positive for metastasis should be resected as well. Surgery alone is inadequate as most dogs will succumb to metastatic disease. Addition of chemotherapy (carboplatin) after surgery may extend the survival time. Chemotherapy alone provides less than a 30% response rate. Coarse-fractionated radiation therapy can also achieve local control (6-8 months). Aggressive surgery with the melanoma vaccine is an option in patients for microscopic disease control. The addition of a DNA tyrosinase vaccine (melanoma vaccine) has yielded improved survival times over traditional treatments, particularly in dogs with local disease control. This option is usually combined with either surgery or radiation therapy. As a group, dogs with stage I-III have a median survival time of 323 days. Negative prognostic factors include size (≥2 cm), lymphatic and/or vascular invasion, high mitotic index (≥3 per 10 hpf), and evidence and metastatic disease.
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Randhurst Animal Hospital
212 East Rand Rd., Mt. Prospect, IL 60056
Veterinarians serving Mt Prospect, Des Plaines, Arlington Heights, Northbrook, Glenview, Morton Grove, Rolling Meadows, Wheeling, Prospect Heights, Palatine and surrounding areas
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