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Venereal sarcoma in dogs
Last reviewed: 05.07.2025
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Most veterinarians classify venereal sarcoma in dogs as an infectious malignant disease and therefore have a second officially accepted name - transmissible sarcoma.
This pathology is also called cloned transmission cancer.
Causes of venereal sarcoma
Transmissible venereal sarcoma, which is found only in the canine family (Canis familiaris) and is distributed globally on all continents, has an unusual pathogenesis that has been seriously studied over the past 130 years.
To date, it has been established that this is a histiocytic tumor of soft tissues, which is transmitted from one animal to another through physical contact (sexually) by histiocytic macrophage cells of the mononuclear phagocytic system (part of the immune system) of the body that develop in the tumor.
That is, tumor cells themselves are infectious agents and, penetrating the tissues of a healthy dog by adhesion, provoke the development of the same tumor. In essence, infection occurs according to the principle of an allotransplant - when cells of one allogeneic individual, entering the body of an individual with a different genotype, take root, and the tumor loses its connection with the original host. It turns out that tumor cells behave like parasites.
Moreover, the cells of tissues affected by venereal sarcoma have fewer chromosomes than normal epithelial cells of dogs (57-64 instead of the required 78).
Domestic veterinarians believe that venereal sarcoma in dogs cannot metastasize, and the appearance of lesions in the mouth and on the muzzle is explained by the simple transfer of infected cells from the genitals during licking. However, foreign specialists say that this tumor metastasizes in about 5% of cases, most often to regional lymph nodes, subcutaneous tissues, eyes, brain, liver, spleen, testicles and muscles.
[ Symptoms of venereal sarcoma
Obvious symptoms of venereal sarcoma begin to appear after a fairly long incubation period (3-6 months after infection of the dog). At first, superficial pink or red nodules 1-3 mm in diameter appear: in males, the tumor affects the base of the head of the penis or the foreskin, in females - the vestibule of the vagina. Then multiple nodules merge, forming larger (up to 50-70 mm) hemorrhagic loose neoplasias, the bumpy surface of which is similar to cauliflower.
Over time, the sarcoma grows into deeper layers of the mucous membrane in the form of a multilobular (multi-lobular) formation, the diameter of which can exceed 100 mm. The tumor bleeds easily, so constant bloody discharge of varying intensity is noted (owners of females may mistake this for estrus). The animal's genitals are deformed, ulcerated and inflamed, in some cases the dog suffers from urinary retention or urethral obstruction.
If the disease has spread to the muzzle (or initially has an extragenital localization), then oral-nasal fistulas, nosebleeds and other nasal discharge, swelling of the muzzle and expansion of the submandibular lymph nodes appear.
Diagnosis of venereal sarcoma
In veterinary clinics, diagnosis of venereal sarcoma is made based on examination of the animal and palpation of the tumor.
A general and biochemical blood test is also performed, and a cytological examination of the material obtained by smearing the affected organs of the dog is performed. As a rule, this is quite sufficient, so a biopsy is performed when the veterinarian has reason to doubt the diagnosis.
Treatment of venereal sarcoma
In modern veterinary medicine, the main method of treating venereal sarcoma in dogs is chemotherapy, since surgical intervention is considered less effective and more risky by most specialists. Although, given the numerous side effects of cytostatic drugs associated with their high toxicity, some doctors consider surgical treatment of this pathology safer - despite the fairly high risk of damage to the urethra and an equally high probability of recurrence of sarcoma from the remnants of unremoved tissue. According to some data, in the case of large invasive sarcomas, the relapse rate can be 55-65%.
The most common cytostatic drugs used for drug treatment of animals with transmissible venereal sarcomas are Vincristine (Vinblastine) and Doxorubicin. The dose of the drug is calculated based on body weight - 0.025 mg per kilogram or from 0.5 to 0.7 mg per square meter of body surface, with a subsequent increase in dosage. As practice shows, males need to undergo intravenous infusion of the drug at least 4-6 times (once a week), females - on average 4 times. However, complete remission may require 7-8 injections
When chemotherapy does not give positive results and the tumor recurs, radiotherapy may be used. After it, male dogs temporarily or permanently lose spermatogenesis.
Prevention and prognosis of venereal sarcoma
Since domestic dogs can become infected through contact with sick stray animals, prevention of venereal sarcoma consists of walking the dog on a leash, monitoring the animal when letting it off the leash for a free walk, in order to prevent accidental mating with other dogs, especially stray dogs.
And if the dog owner was not paying attention, then veterinarians recommend in such situations to treat the mouth, muzzle and genitals with disinfectants: 0.05% solution of chlorhexidine bigluconate, iodine (0.1%), furacilin solution (0.1 g per 0.5 l of hot water), potassium permanganate solution (0.02-0.1%) or 2-5% resorcinol solution.
Foreign veterinary medicine specialists claim that the prognosis of venereal sarcoma largely depends on the state of the animal's immune system, and a strong immune response can lead to spontaneous regression of the tumor. Moreover, studies have shown that antibodies recognizing antigens of transmissible venereal sarcoma are often found in the blood serum of dogs that have recovered from the disease.
According to statistics from the American Veterinary Medical Association (AVMA), complete remission of venereal sarcoma in dogs occurs in more than 90% of cases, and with treatment of the disease in the early stages and the absence of metastases, 100% remission is possible.