Tumors of the Penis and Prepuce in Dogs

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Overview of Tumors of the Canine Penis and Prepuce

Tumors of the penis are rare in the dog, but preputial tumors are more common. Tumors that occur on the prepuce are similar to the tumors that grow on other haired regions of the body. Some of the most common preputial tumors include mast cell tumors, squamous cell carcinomas, papillomas and fibromas.

The most common penile tumors are transmissible venereal tumors (TVT). Other tumors, including squamous cell carcinoma and adenocarcinomas occur much less frequently, but have been reported. Primary tumors of the urethra, especially transitional cell carcinomas, may occasionally extend into the penis.

Penile and preputial tumors typically occur in older dogs, with the exception of transmissible venereal tumor. Transmissible venereal tumors are contagious and are spread by direct contact.

Boxer dogs seem to have a higher incidence of skin tumors than most dogs. Dogs at risk for transmissible venereal tumors include breeding animals or intact male dogs allowed to roam freely.

What to Watch For

Many dogs with preputial tumors are not symptomatic. If signs are present, they usually include:

  • A mass or swelling on the penis or prepuce
  • Discharge (occasionally bloody) from the prepuce or penis
  • Excessive licking of the penis
  • Foul odor
  • If the tumor is causing a compressive lesion or blockage of the urethra, dogs may strain to urinate and become quite ill.
  • Diagnosis of Tumors of the Penis and Prepuce in Dogs

  • A complete physical examination
  • Complete blood count (CBC)
  • Biochemical profile
  • Urinalysis with or without culture
  • Chest and abdominal radiographs (x-rays)
  • Impression smear of a penile mass
  • Biopsy of the mass
  • Aspiration (inserting a needle and syringe into the tissue and obtaining a small sample of cells) and cytology (microscopic analysis of the cells) of the mass
  • Treatment of Tumors of the Penis and Prepuce in Dogs

  • Surgical excision
  • Chemotherapy
  • Radiation therapy
  • Home Care and Prevention

    Watch the incision daily for any sign of swelling or discharge. If skin sutures are used, they should be removed in 7 to 10 days. If your dog begins to lick the area excessively, an Elizabethan collar designed to prevent licking at incisions may be required. Seek veterinary care if your dog has a fever, is feeling ill post-operatively, is straining to urinate or seems painful when urinating.

    If treating TVT, limit exposure to other dogs until the tumor has regressed. If chemotherapy is being used, periodic blood tests will need to be checked.

    Animals should be re-evaluated periodically for signs of recurrence. The only tumor where preventive measures may help is TVT.

    An excellent preventive measure is to have your dog neutered at an early age. Do not allow dogs to roam freely.

    In-depth Information on Canine Tumors of the Penis and Prepuce

    Tumors that involve the prepuce of the dog are similar in type and biologic behavior to tumors found elsewhere on a dog’s skin. Most of these tumors are not causing clinical problems for the dog at the time of their discovery. Occasionally they may ulcerate, bleed, itch or cause discomfort, and require more immediate attention, but usually they are found incidentally on routine examinations by veterinarians or by their owners.

    Tumors of the penis usually cause more clinical signs, in general, and are more uncomfortable. Masses on the penis are irritating and cause excessive licking of the area. Some tumors (especially TVT) may be quite friable (small pieces may break off), and bleeding may be seen. Secondary infections may also be associated with penile tumors, often producing a foul smell. If the tumor is located near the urethral opening, the flow of urine may be inhibited, leading to straining to urinate. If the blockage is severe enough a urinary obstruction could occur, leading to an emergency situation and potential kidney damage. Fortunately this is a rare occurrence.

    The most common penile tumor is TVT and is the tumor that is mostly preventable. TVT is transmitted as tumor cells break off from the main tumor and are transplanted into susceptible tissue. Dogs contract TVT this way through sexual contact with infected dogs or from licking and smelling the tumors. It is for this reason that dogs will often have transmissible venereal tumors on their nose or lips. Neutering animals and decreasing exposure to stray dogs will help decrease its incidence significantly.

    Other diseases that may cause similar clinical signs as tumors of the penis and prepuce include:

  • Normal penile erection. A normal erection may be misinterpreted as a tumor if one is not familiar with the normal canine anatomy. The dog has a gland in the base of his penis (bulbus glandis) that swells, and becomes a hard spherical swelling. It is often confused with a penile tumor the first time it is seen.
  • Urethritis and cystitis are inflammatory conditions of the urethra, which is the tubular structure that carries urine from the bladder through the penis, and bladder. Both conditions may cause discomfort, straining to urinate, discharge from the penis and excessive licking.
  • Prostatic disease can also cause a penile discharge that can be bloody. A rectal exam should always be done to evaluate the size and shape of the prostate.
  • Balanoposthitis is inflammation of the penile and preputial surface. This is a fairly common but not serious condition present in intact male dogs. Dogs with the problem may have a large amount of discharge from the penis, and lick the area excessively.
  • Infected wounds or dermatitis on the prepuce may occasionally appear as ulcerated swellings on the surface of the prepuce, and might be confused with preputial tumors.
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