Oral Melanoma

Question 1

What is the most common malignant oral tumors in dogs?

Answer 1

melanoma

Question 2

What is the top breed prone to developing oral melanomas? What are some other breeds?

Answer 2

Chow Chow

• Golden Retrievers
• Poodles
• Cocker Spaniels

Question 3

What are 2 diagnostic challenges when diagnosing an oral melanoma?

Answer 3

1. morphologically can look like neoplasms of mesenchymal, epithelial, or round cell origin
2. 1/3 are amelanotic

Question 4

How do most oral melanomas behave?

Answer 4

a majority are metastatic and metastasize to local lymph nodes and lungs

Question 5

What are 2 other locations it is common to find melanomas? How do they compare to oral melanomas?

Answer 5

1. cutaneous - more commonly benign
2. nail beds - 50/50 malignant vs. benign

Question 6

What is required to definitively diagnose oral melanomas? What 3 things are included in staging?

Answer 6

biopsy

1. minimum database - CBC/Chem
2. regional lymph node aspirates
3. thoracic radiographs
   +/- CT/MRI for bone involvement and surgical planning

Question 7

What is the treatment of choice for oral melanomas? What if this is not an option?

Answer 7

surgical excision with wide margins, typically requiring removal of underlying bone (partial mandibulectomy or maxillectomy)

radiation therapy

Question 8

What adjuvant therapies are recommended in cases or oral melanomas?

Answer 8

• chemotherapy
• immunotherapy

Question 9

What chemotherapy agents have shown mild efficacy in slowing the development of oral melanomas?

Answer 9

platinum agents - Carboplatin, Cisplatin

Question 10

What immunotherapy is available for treating melanomas? How does it work? When is it most useful?

Answer 10

xenogenic human DNA vaccine - ONCEPT

• injected DNA encodes for human tyrosinase that is recognized by the dog’s immune system as a foreign antigen causing the dog to form antibodies against it
• similarities between human and canine tyrosinase cause the antibodies to crossreact and bind with canine tyrosinase as well, creating an immune response to the melanoma cells

AFTER the melanoma has developed, NOT to prevent disease from developing

Question 11

What are 3 variables that alter prognosis with oral melanoma?

Answer 11

1. tumor size - <2cm = MST of 17 months, >2cm = 5.5 months
2. cleanliness of margins obtained with the first surgery
3. tumor location - rostral oral cavity = longer MST, caudal oral cavity = shorted MST