Melanoma

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Article Written by Dr. Daniel A. Degner, Board-certified Veterinary Surgeon (DACVS)

Animal Surgical Center of Michigan

5045 Miller Road

Flint, MI 48507

www.animalsurgicalcenter.com

Phone: 810-671-0088

Key Points

Melanomas located in the mouth, lips and toenail bed usually are very malignant

Melanomas located in haired skin generally are benign

A combination of surgery and adjunctive therapy such as melanoma vaccination, radiation and/or chemotherapy may be recommended

Prognosis for malignant melanomas is guarded, but newer treatments are giving hope for long-term survival


Melanomas

Melanoma is a tumor that can develop in the skin, toe nail bed, lips, eye, intestine and other unusual places. These tumors originate from the pigment-producing cells called melanocytes. These cells are responsible for giving humans a tan with sun exposure. Melanomas located on the haired skin (except the toenail bed) generally usually do not spread to other organs. Of all digital tumors, 17.3% have been reported to be melanomas. These tumors have a very high spread rate. At the time of diagnosis of a digital melanoma, roughly one-third of dogs will have detectable of the tumor spread to the lungs. Melanoma is the most common oral tumor. This tumor is locally invasive and spreads rapidly to the regional lymph nodes and lungs. Certain types of melanomas on the lips and oral cavity have a very low tendency to spread and have a very good chance to be cured with surgery.

 

Signs

A brown or black mass (lump) is the most common sign of a melanoma. Some melanomas are not pigmented and may appear as a pink mass. A melanoma in the oral cavity may produce signs of drooling, bad breath, reluctance to chew hard food, blood coming from the mouth and a black or pink mass in the mouth. A melanoma that involves the toenail bed may cause the toe to swell and may cause lameness. Initially, this tumor of the digit may mimic the appearance of an infected toe; however, treatment with antibiotics does not resolve the problem. Enlargement of lymph nodes in the area of the tumor may be a sign of spread of the tumor to these nodes. If the patient has spread of tumor to the lungs, potential clinical signs may include breathing difficulty, coughing, weight loss, poor appetite and malaise.

 

Diagnosis

The diagnosis of a melanoma is based upon a fine needle biopsy or surgically collecting a piece of tissue from the mass. If the fine needle biopsy does not provide a definitive diagnosis, a core of tissue may be required. A complete blood count, chemistry profile and urine testing are done to evaluate the health status of your companionís internal organs prior to anesthesia and surgery. Chest x-rays are used to help rule out spread of cancer to the lungs and lymph nodes in the chest. Abdominal ultrasound is also performed to rule out spread of tumor to the internal abdominal organs. Lymph nodes in the area of the tumor are evaluated with a fine needle biopsy to rule out spread of the cancer. If this test does not provide a clear-cut answer, removal and microscopic analysis of a regional lymph node is recommended.

 

The day of surgery

Our anesthesia and surgical team will prescribe a pain management program, both during and after surgery that will keep your companion comfortable. This will include a combination of general anesthesia, injectable analgesics, local anesthetics, oral analgesics and anti-inflammatory medication. The surgeon will call you with an update after surgery.

 

Treatment

Surgery is an essential treatment for a melanoma. If the tumor is located on the toenail bed, amputation of the entire toe is essential. Tumors located in the oral cavity require an aggressive surgery to remove all local disease. Commonly, these tumors invade into the bone; therefore, a portion of the jawbone must be removed with the tumor to achieve local control of the disease. Melanomas located in the haired skin (except for the nail bed) typically are benign and only require conservative simple surgical removal. In certain cases, an oncologist may recommend chemotherapy for melanomas. Typically, one treatment is performed every 3 weeks for a total of 4 to 6 treatments. Most patients tolerate the chemotherapy medication with transient mild side effects. Radiation therapy has been shown to prevent or delay the onset of tumor regrowth. Eighteen to 21 radiation treatments are administered to the tumor site and regional lymph nodes, starting 2 weeks after the tumor has been removed. Radiation treatments are administered Monday through Friday with no treatment during weekends. A short anesthesia is required to administer each radiation treatment. A melanoma vaccine, which requires administration of a series of injections, can help the body to kill residual tumor cells. Best results are achieved when all visible tumor has been removed.

 

Aftercare

After surgery, a prescribed pain reliever should be given to minimize discomfort. Itís also extremely important to limit your companionís activity and exercise level for three weeks after surgery. The incision should be checked daily for signs of infection. Two weeks after surgery, the surgeon will monitor the healing process and our oncologist will initiate adjunctive therapy (melanoma vaccination, chemotherapy or radiation therapy), if indicated by the biopsy report.

 

Results

Oral melanomas: The size of a melanoma and stage of the disease (presence of metastasis) directly affects the survival time. Patients with stage 1 tumors (less than a 2 cm diameter mass and no metastatic disease) that are surgically removed have medial survival times of 17 to 18 months. Patients with stage II tumors (2 cm but less than 4 cm in diameter mass with no metastasis) that are surgically removed have median survival times of 5 to 6 months. Patients with stage III tumors (4 cm and larger mass with spread to regional lymph nodes) have median survival times of 3 months. Stage IV tumors are those that have already spread to distant sites such as the lungs and survival times are weeks to a few months.

Negative prognostic factors include advanced stage of the disease, evidence of metastasis and the mitotic index on the biopsy report. Death of the patient is usually due to metastatic disease (spread of tumor) typically to the lungs.

Radiation therapy has been reported to have excellent local control of oral melanomas, yet does not prevent or treat the spread of the tumor to the lungs and other distant sites. Therefore, this modality should be used in conjunction with the melanoma vaccine for improved survival times.

Vaccination with the melanoma vaccine reportedly gave excellent long-term control of the disease and survival times. Bergman reported only minimal to no side effects, which at worst was mild local reaction at the injection site. The best result was seen with intradermal vaccination that must be administered with a special injector system. Currently, their published data was limited to 9 dogs treated with surgery and melanoma vaccine in dogs in which one dog with stage IV disease had complete resolution of tumors in the lungs for 329 days. Two dogs that had stage IV disease had survival times of 421 and greater than 588 days. Two dogs that had stage II/III disease had survival times of 501 and 496 days. Four of nine dogs had no positive response to the vaccine. Digital melanomas: Digital melanomas treated with surgical amputation of the digit resulted in a median survival time of 365 days. Digital melanomas that are not located on the nail bed and have benign characteristics (low mitotic index) can be potentially cured with surgery alone. Skin melanomas: Melanomas that are located in the skin (except for the nail bed) carry an excellent prognosis with simple surgical removal or digit amputation, as they have a very low spread rate.

 

References

  1. Esplin DG. Survival of dogs following surgical excision of histologically well-differentiated melanocytic neoplasms of the mucous membranes of the lips and oral cavity. Vet Pathol. 2008 Nov;45(6):889-96.
  2. Bergman PJ, et al. Development of xenogeneic DNA vaccine program for canine malignant melanoma at the Animal Medical Center. Vaccine. 2006 May 22;24(21):4582-5.
  3. Bergman PJ, et al. Long-term survival of dogs with advanced malignant melanoma after DNA vaccination with xenogenic human tyrosinase: a phase 1 trail. Clin Cancer Res 2003 Apr; 9(4):1284-90.
  4. Bergman PJ. Canine oral melanoma. Clin Tech Small Anim Pract. 2007 May;22(2):55-60.
  5. Wobeser BK, et al. Diagnoses and clinical outcomes associated with surgically amputated canine digits submitted to multiple veterinary diagnostic laboratories. Vet Pathol. 2007 May;44(3):355-61.
  6. Williams LE, et al. Association between lymph node size and metastasis in dogs with oral malignant melanoma: 100 cases (1987-2001). J Am Vet Med Assoc. 2003 May 1;222(9):1234-6.
  7. Blackwood L, et al. Radiotherapy of oral malignant melanomas in dogs. J Am Vet Med Assoc. 1009 Jul 1:209(1):98-102.
  8. Marino DJ, et al. Evaluation of dogs with digit masses: 117 cases (1981 -1991). J Am Vet Med Assoc. 1995 Sep 15;207(6):726-8.

Frequently Asked Questions After Surgery

When should my dog have the first bowel movement after surgery?

  • Many dogs will not have a bowel movement for the first 4 to 5 days after surgery
  • Reasons that a dog will not have regular bowel movements after surgery include:
    • The dog has been fasted prior to surgery
    • Dogs do not eat well during the hospital stay
    • They frequently do not eat well when they go home
    • They are fed highly digestible food that produces little stool
    • Pain medication that contain narcotics (such as morphine, fentanyl patches, and tramadol) can be constipating
  • If a pet does not have a bowel movement on the 5th day of being home, a stool softener such as metamucil can be fed
    • Dose of metamucil is 1 tsp per 25 Kg mixed in with each meal (canned dog food); feed immediately after mixing, as the metamucil will gel the food and may make it less palatable

My pet had surgery and will not eat.  What can be done?

  • Dogs
    • Most pets will not eat their regular dog food after surgery, especially if it is kibble.
    • Offer a cooked diet having a 1:1 ratio of a protein source and carbohydrate source.  The protein source can be any meat (example: chicken breast, turkey breast, lean hamburger) that is low in fat and should be cooked (drain off all fat after the meat has been cooked).   The carbohydrate can be pasta, potato or white rice.
    • Try canned dog food; to enhance the flavor sprinkle a very small amount of garlic powder or chicken or beef broth (Chicken-in-a- MugTM or Beef-in-a-MugTM products)
    • Try Gerber strained meats for babies such as the chicken, beef, turkey, or veal
    • Try Hill's A/D diet available at most veterinary hospitals
    • Hand feeding: place a small amount of food in the mouth so that your dog gets the flavor
    • Warm the food slightly in a microwave, as the food will be more aromatic; stir the food before feeding and test the temperature on the bottom side of your wrist; it should only be luke warm.
    • Remember that most pets will not eat the first day or two after they get home from surgery
  • Cats
    • Offer smelly foods that contain fish such as tuna or smelly cat foods
    • Try Gerber strained meats for babies such as the chicken, beef, turkey or veal
    • Hand feeding:  with your finger place a small amount of food on the roof of your cat's mouth; use a syringe to get soft food into the mouth
    • Warm the food slightly in a microwave as the food will be more aromatic; remember to stir the food before feeding and test the temperature; it should be only luke-warm
    • Some cats will only eat dry food, try kibble if your cat normally has been fed that food
    • Petting and stroking your cat frequently will help to stimulate appetite
    • Remember that most pets will not eat the first day or two after they get home from surgery
    • Appetite stimulants such as cyproheptadine may be helpful
    • If your cat refuses to eat anything for 7 days a stomach tube or nasogastric tube should be placed to provide nutrition so that a serious liver problem (hepatic lipidosis) does not develop

My pet is vomiting.  What can be done?

  • The first thing for you to discern is whether your pet is vomiting or regurgitating.  Both will result in fluid or food being brought up.  Vomiting always will have heaving or retching of the abdomen prior to expulsion of the vomitus.  Regurgitation is not associated with heaving and the pet usually just opens the mouth and fluid or food will be expelled.  Usually the regurgited material will be clear or brown colored fluid. 
  • Next is to identify the cause of the vomiting or regurgitation.
  • Causes and treatment of vomiting after surgery
    • When some pets return home after a stay in the hospital they may drink excessive amounts of water at one time and then vomit; if this appears to be the case, the water should be limited to frequent smaller amounts.
    • Medications such as antibiotics, narcotics or nonsteroidal anti-inflammatory medication commonly cause vomiting after surgery.  In order to see which medication is causing the problem, the administration of each drug should be separated 2 hours apart.  Usually the pet will vomit or appear nauseated (drooling and sick look) within 1 hour of administration of the medication that they are sensitive to.  The antibiotic in some cases may be changed to a different one, or may be discontinued. 
    • Stomach upset from anesthesia is a potential cause of vomiting and will pass within a couple of days. 
    • An uncommon cause of vomiting after surgery is internal organ failure.  Blood testing will confirm this problem. For this reason vomiting should not be ignored if it persists for more than 24 hours.
    • If your pet had surgery of the bowels or stomach, vomiting is always a concern, as it may indicate that infection of the abdominal cavity, called peritonitis, is present.  Do not ignore this sign.
    • Symptomatic treatment of vomiting involves withholding food for 12 to 24 hours, then introducing small amounts of bland food such as rice and lean cooked hamburger, if your pet does not vomit after that then gradually wean him/her back onto the regular diet after 3 days.  In order to decrease the acidity of the stomach, Pepcid AC 0.5 mg/kg can be given by mouth twice daily for 5 days.  Metoclopramide and Cerenia are good anti-vomiting medications for dogs and cats.  You should always consult a veterinary healthcare professional before administering medication.
  • Causes and treatment of regurgitation after surgery
    • The most common cause of regurgitation is reflux of acid from the stomach into the esophagus while your pet is under anesthesia.  Acidic fluid from the stomach can cause a chemical burn of the esophagus and result in a bad case of heart burn, called esophagitis.  This results in poor motility of the esophagus, therefore water and food will accumulate in this structure.  In most cases, esphagitis is self-eliminating and will resolve within two or three days. 
    • If the esophagitis is severe the esophagus may develop one or more strictures.  A stricture is a narrowing or stenosis of the esophagus and does not allow passage of food down the esophagus, in regurgitation that lasts longer than one week.  This problem should be brought to the attention of your pet's doctor within the first two weeks so that it can be treated by ballooning the stricture (minimally invasive procedure, as it is done with the aide of an endoscope).  If an esophageal stricture is chronic surgery is needed.
    • Symptomatic treatment of regurgitation caused by esophagitis includes feeding bland food, and administering a coating agent (sucralfate) and an acid blocker (omeprazole or other).  Consult a veterinary health care professional if the regurgitation continues for more than a couple of days.

How do I know that my dog is in pain following surgery?

  • Signs of pain include
    • crying
    • biting if you get near the surgical site
    • grimacing (lips are pulled back and the the dog looks anxious)
    • tragic facial expression
    • panting
    • restlessness and unable to sleep; pacing
    • if abdominal surgery was done the pet will not lie down on the incision, or will continually sit up in spite of appearing very tired
    • the worst pain will be for the first 2 to 3 days after surgery

What can I do to control my dog's pain?

  • Narcotic medications that control pain: tramadol, butorphanol, Duragesic (fentanyl patch)
  • Anti-inflammatories used to control pain: Deramaxx, Rimadyl, Previcox, or Etogesic
  • If an orthopedic surgery has been done cold packing the surgical site may be helpful
    • A cold pack may be a pack of frozen peas, crushed ice in a Ziploc bag, or a cold gel pack; place a thin barrier between the skin and the cold pack.  An alternative to a cold pack is to freeze water in a styrofoam cup; after frozen cut the bottom of the styrofoam cup out. Cool the surgical site around the incision by rubbing the exposed ice directly on the skin in a circular pattern.  Cooling the surgical site helps to numb the area.

How do I know that my cat is in pain following surgery?

  • Pain is more difficult to assess in cats versus dogs, as signs can be more subtle and they usually do not vocalize when in pain
  • Signs of pain in a cat include the following:
    • biting if you get near the surgical site
    • growling or deep cry
    • not wanting to eat
    • hiding and not wanting to be near owner (remember that this could also be caused by the cat just being upset about leaving home and coming back)

What can be done for pain at home for my cat?

  • Pain medication such as buprenorphine or a Duragesic (fentanyl) patch
  • Tylenol will kill a cat as they lack abundant glutathione enzyme in the liver
  • Anti-inflammatories can be used, but the dose is much less than dogs

Is it okay for my pet to lick the incision?

  • If a dog licks the incision, the healing process may be delayed.
  • Licking can remove stitches and cause the incision to open
  • Licking can become a severe habit that is difficult to break
  • Licking can cause infection as the mouth has many bacteria
  • Dogs will frequently lick the incision when the owner is not watching such as at night time; if the skin looks red or excoriated the most common cause is from licking.
  • To stop your pet from licking the following can be tried:
    • Elizabethan collar can be placed on the neck; this will not help stop your pet from scratching at the region
    • Cervical collar (bite not collar) is a less awkward device and can be effective at stopping a pet from licking the surgical site
    • A tee shirt can be used to cover an incision on the chest or front part of the abdomen; gather the waist of the shirt up over the dog's back and wrap an elastic band around this part of the shirt.
    • A bandage or sock can be used to cover an incision on a limb; fasten the top of the sock to the dog's limb with tape.
    • Bitter apple can be applied around the incision; many dogs will continue to lick  after application of this topical
    • Bitter Apple and Liquid HeetTM (obtain this from a drugstore...it is used for sore muscles) mixed in a 2:1 ratio can be applied around the skin incision
    • Antipsychotic medication in some cases is needed

Board-certification by the American College of Veterinary Surgeons

What does it mean?

  • Four years of advanced training in surgery beyond the Doctor of Veterinary Medicine Degree

  • Experience in the development of new surgical treatments

  • Rigorous examination by the American College of Veterinary Surgeons to ensure competency in advanced surgical techniques

  • Assurance that a veterinarian is a surgical specialist

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