Information

Prostate cancer in dogs


Prostate cancer in dogs is a disease of large breeds and occurs with an early onset and a poor prognosis.

The prognosis is generally poor when it is accompanied by metastatic disease.

The survival times and quality of life of the patient is likely to be influenced by the aggressiveness of the disease and the patient's general condition.

The mean life span of the dog after the disease is detected is 13 weeks, or 8.7 weeks of quality of life.

The clinical signs associated with this cancer are:

a large firm tumour that grows slowly over many months, with a painless ulcerative mass

a painful swollen bladder, and/or kidney failure in old dogs

a frequent discharge of a greenish-yellow liquid

urinary tract disorders

hind limb pain, which may become more frequent and pronounced with age

anemia and/or thrombocytopenia.

Causes

Prostate cancer is caused by genetic factors and lifestyle.

Prostate cancer may be hereditary. There is a greater risk if the parents and siblings of affected animals have developed the disease.

Lifestyle and environmental factors may also contribute to the development of prostate cancer.

Diagnosis

A diagnosis of prostate cancer in dogs is made on the basis of the clinical and pathologic characteristics of the lesion.

Pathology

Tumour mass, on gross examination, is firm, with an irregular surface, and ranges from 3 to 5 cm in diameter.

The cut surface of the tumour often shows necrosis, liquefaction and hemorrhage.

The normal prostatic gland is lobular. The lesions of this cancer have a similar appearance, with a lobular growth pattern.

Lymphadenopathy is very common.

On microscopic examination, adenocarcinomas are characterized by neoplastic glands lined by a single layer of cells and supported by the stroma.

Hematoxylin and eosin stains show neoplastic cells with the following characteristics:

clear to lightly basophilic cytoplasm,

moderate variation in nuclear size and shape,

a vesicular nucleus with evenly dispersed chromatin, and

no visible nucleoli.

Immunohistochemical stains are helpful in differentiating tumours of a few other types.

Staining with antibodies to prostate specific antigen may help to confirm the diagnosis.

Differential Diagnosis

Prostate cancer is easily distinguished from benign prostatic hyperplasia, because these two conditions cause different clinical signs and have a different histologic appearance.

Benign prostatic hyperplasia is a common disease in older male dogs. The lesions are nodular and multifocal. The stroma is fibrous, and the lesions are less often accompanied by fibromuscular dysplasia.

Prostate cancer has no benign counterpart.

Prostatic cysts are usually benign and should not be mistaken for prostate cancer. Cysts have a thin, pseudostratified, non-keratinized lining of cuboidal to flattened cells, while carcinomas have a much thicker, more proliferative lining of columnar cells. The stroma of a cyst is typically fibrous, but the stroma of a carcinoma is not fibrous, as its structure is disorganized.

Prostate cysts are most often bilateral, while prostate cancer is usually unilateral.

Cystitis is a possible cause of inflammation of the prostate.

Uveitis is a possible cause of inflammation of the prostate.

Inflamed prostates may be mistaken for prostate cancer by cytologic examination or by biopsy. However, inflammatory changes may be focal and limited, with no evidence of more widespread disease.

Diagnosis and Treatment

Diagnosis is based on examination of the prostate and biopsy.

The prostatic ducts are readily identified during the clinical examination. The presence of hematuria is of little or no significance.

Treatment is based on the type and severity of the prostatic disease.

Prostatic nodules or cysts should be removed by surgery.

Hemorrhage, a common and serious complication of prostatectomy, should be controlled by administration of a prostatic-specific antifibrinolytic, eg, danazol.

When possible, surgical removal should be used to treat prostatic cancer. In a small percentage of cases, cancer is so limited that the tumor is cured by surgery. In many other cases, the initial treatment is cytoreduction, which eliminates most of the visible tumor and any microscopic disease, leaving only microscopic disease, which is unlikely to cause clinical problems in the short term.

Cytoreductive surgery is performed with a technique known as the total perineal prostatectomy, in which the gland is excised and the urethra is reconstructed with a segment of bladder.

Radiation therapy may be used in patients with localized prostate cancer, particularly those with a Gleason score of 7 or less. Radiation should be combined with androgen deprivation in patients with evidence of metastatic disease.

For patients with large, extensive disease with a Gleason score of more than 7 or with rapidly growing tumors, androgen deprivation alone may be the most effective treatment. This therapy has a definite survival benefit, although most men develop androgen-resistant disease during this treatment.

The value of chemotherapy for the treatment of prostate cancer is still being investigated.

Prognosis

Prognosis is related to the tumor grade (Gleason score), tumor stage (clinical and pathologic), and the type of treatment used. The overall 5-year survival is 75% to 90% for patients with localized disease, and 5% to 20% for those with disseminated disease.

Some investigators believe that if a patient's tumor is diagnosed and treated before it reaches a size that cannot be removed by surgery, the 5-year survival rate can exceed 95%.

Most patients are followed every 3 to 6 months for the first 2 years and every 6 months after that. This includes a digital rectal exam and a prostate-specific antigen (PSA) test. PSA measurements are sometimes used to screen for possible recurrence. Additional tests are done if the results of these examinations are abnormal.

The incidence of the condition increases with age. According to the American Cancer Society, one in six men will develop prostate cancer during his lifetime.

The cause of prostate cancer is not yet understood. Many risk factors have been identified, but none seem to account for more than a small percentage of cases. Some risk factors have been shown to be related to other cancers in men.

Researchers have found that African-American men are more than twice as likely as white men to develop the disease, and they have a poorer survival rate than white men.

There is a lower incidence of prostate cancer among Asian men and other men who live in colder climates. Researchers think that a possible explanation for this is that they eat diets that include a lot of vegetables and fruits, which help prevent the development of prostate cancer.

Most prostate cancers are slow growing. Most men with early-stage prostate cancer have a long life without symptoms. In the case of more advanced-stage cancer, symptoms can include difficulty urinating, blood in the urine, painful urination, inability to urinate, and pelvic pain.

Because it is the largest organ of the body and has so many functions, even small, early-stage prostate cancers can cause symptoms. Most cancers grow at an extremely slow rate, and


Watch the video: Veterinary tip of the day - Canine Prostatic Enlargement (January 2022).

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