Malignant Melanoma - Oral

A highly malignant tumour that is locally aggressive and spreads to other parts of the body. 

Overview

A tumor that affects middle age to older dogs and involves the pigmented skin cells, melanocytes. It is a serious condition that is potentially deadly.

Melanomas can be benign or malignant. Tumor behavior is highly dependent on the region where it develops. 

Benign tumors

Benign tumors are well differentiated from the surrounding tissue, making them easier to remove surgically.

Malignant tumors

Malignant melanomas can be locally aggressive or spread to other areas of the body such as the lungs and liver.

Unfortunately, oral melanomas are particularly aggressive.

Staging of Oral Melanoma

Stage I	tumor less than 2 cm
Stage II	tumor 2-4 cm in diameter
Stage III	tumor 4 cm or larger with local lymph node involvement
Stage IV	tumor with distant spread to other organs

Diagnosis

• Biopsy
• Staging
• Radiographs of chest
• Check local lymph nodes
• Ultrasound of abdomen

Treatment

1. Local Disease Control

The surgical removal of the disease. However, the location often makes it difficult for a full resection, so another treatment is often prescribed e.g. radiation or chemotherapy.

2. Destruction of undetectable tumor cells in the process of spreading

Chemotherapy and immunotherapy help reach malignant cells that are in transit, circulating the body.

3. Removal of cancer detectable in other organs

This is seen in Stage IV cases, where cancer is found in another site in the body. Chemotherapy, although not notoriously effective, is often prescribed to give an average survival time of 30-119 days.

The Melanoma Vaccine

A melanoma vaccine has been found to be useful with other forms of treatment such as surgery for oral melanomas and toe melanomas. The vaccine helps to generate an active immune response against the existing tumor cells. It has been trialed and used extensively in Stage II and III cases but may not be helpful in Stage IV cases where the tumor has already spread. 

Prognosis

Oral melanoma survival time

Stage I	approximately 17-18 months (with surgery alone)
Stage II	approximately 6 months (with surgery alone)
Stage III	approximately 3 months (with surgery alone)
Stage IV	approximately 1 month (surgery not applicable)

The goal of additional adjunctive therapy (radiation, chemotherapy, immunotherapy) is to extend this time.