Digital Tumors

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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

The most common type of tumors of the toe is squamous cell carcinoma and melanoma

Surgical amputation of the affected toe is the treatment of choice

Prognosis generally is very favorable for squamous cell carcinoma and fair for melanoma


Anatomy

The digit is commonly known as the toe. Each digit has 3 phalanges bones. The nail bed is attached to the third phalange bone.

 

 

Digital tumors

Tumors of the digits (toes) most commonly include squamous cell carcinoma, melanoma, osteosarcoma, hemangiopericytoma, benign soft tissue tumors and malignant soft tissue tumors. Squamous cell carcinoma accounts for more than 50% of all digital tumors. This tumor, which originates from skin cells, is very locally invasive and commonly will destroy the bone in the digit (see photo below left). Melanoma, the second most common tumor, accounts for 16% of all digital tumors. These tumors originate from the pigment-producing cells in the skin called melanocytes. These cells are responsible for giving humans a tan with sun exposure. Melanomas of the nail bed spread rapidly to other areas of the body. At the time of diagnosis of a digital melanoma, one-third of all affected dogs will have detectable spread to the lungs. Melanomas of the digits that do not involve the nail bed and are confirmed to be benign on the biopsy usually do not metastasize (see photo below right).

 

 

Signs

Squamous cell carcinoma is most commonly seen in large breed dogs with black coats. Over-represented breeds include Labrador Retrievers and Standard Poodles. Digital tumors will cause the toe to swell (see photo right) and may cause lameness. Initially, a tumor of the digit may mimic the appearance of an infected toe; however, treatment with antibiotics does not resolve the problem. If the tumor appears to be darkly pigmented, a melanoma is more probable; however, some melanomas lack pigment and may mimic the appearance of a squamous cell carcinoma. Enlargement of lymph nodes in the area of the tumor may be a sign of spread of the tumor to these nodes. If the tumor has spread to the lungs, potential clinical signs may include breathing difficulty, coughing, weight loss, poor appetite and malaise.

 

 

Diagnosis

The diagnosis of a digital tumor 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 companion’s internal organs prior to anesthesia and surgery. X-rays of the affected digit may show destruction of the bone, especially if the tumor is a squamous cell carcinoma. Chest x-rays are used to help rule out spread of the cancer to the lungs and lymph nodes in the chest (see x-ray right which shows spread of melanoma tumors to the lungs). 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 aspirated to rule out spread of the cancer to the nodes, regardless of whether they are enlarged or not. If this test does not provide a clear-cut answer, removal of a regional lymph node and analysis of the node by a pathologist 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 a progress report following the surgical procedure.

 

 

Treatments

Surgery is essential to treat a digital tumor. If the tumor is located on the toenail bed, the entire toe must be amputated. In some cases, benign tumors of the skin of the digits may be removed without removing the digit. Adjunctive therapy (chemotherapy or radiation) may be indicated for some malignant tumors. Usually surgery is all that is needed for a squamous cell carcinoma, however, melanomas should be treated more aggressively with a melanoma vaccination, chemotherapy and/or radiation.

An oncologist may recommend chemotherapy for your companion. Typically, one treatment is administered 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 during administration of each radiation treatment.

 

 

Aftercare

After surgery, a prescribed pain reliever should be given to minimize discomfort. Exercise must be limited for three weeks after surgery so that uncomplicated healing can take place. For one week, a bandage likely will be placed on the operated limb to protect the incision. Thereafter, 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 radiation therapy if indicated by the biopsy report. The oncologist may also recommend chemotherapy in selected cases. Melanoma vaccine can be administered as soon as a diagnosis of melanoma has been established.

 

 

Results

Digital melanomas: Digital melanomas treated with surgical amputation of the digit have a median survival time of 365 days. Digital melanomas that are not located on the nail bed and have benign characteristics (low mitotic index) on the biopsy are commonly cured with surgery alone. Inoculation with the melanoma vaccine can provide excellent long-term control of the disease and increased survival times for melanomas. Bergman reported only minimal to no side effects, which at worst was mild local reaction at the injection site. The best result is seen with intradermal vaccination that must be administered with a special injector system (see photo right of a intradermal vaccination). Squamous cell carcinoma: In a series of 21 cases, only 1 dog had local recurrence of the tumor and another dog developed metastasis of the tumor to the lungs after surgery. Therefore, this tumor has a very good chance to be cured with surgery alone.

Short-term complications following surgery are uncommon and may include temporary dehiscence (opening) of the incision and infection. Tumor recurrence and spread of cancer are other complications. Rarely, amputation of a digit will cause ongoing lameness on the operated limb.

 

 

References

  1. Henry CJ, et al. Canine digital tumors: a veterinary cooperative oncology group retrospective study of 64 dogs. J Vet Intern Med. 2005 Sept-Oct;19(5):720-4.
  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. 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.
  5. O’Brien MG, et al. Treatment by digital amputation of subungual squamous cell carcinoma in dogs: 21 cases (1987 - 1988). J Am Vet Med Assoc. 1992 Sep1;201(5):759-61.

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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