Tumors of the penis are rare in the dog, but preputial tumors are more common. Tumors of the penis and prepuce in cats are extremely rare.

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 animals 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

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

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.