Mammary tumors are benign or malign lumps of the mammary glands. They are the most commonly seen tumors of unsterilized female dogs and usually affect older individuals.


Urgency level 3


Danger level 4


Young she-dogs are usually untroubled by this disease. It mainly appears after exceeding the seventh year of life and appears increasingly with old she-dogs (older than 10 years). The tumors either appear individually or in groups. They are nothing else than increased tissue growth (lumps) in the area of the mammary line which can reach a diameter of handball size. They are rather compact elastic and the surface is not even, but crooked. The animal normally does not feel any pain in case of pressure. The skin above the tumors can be displaceable or not displaceable. Additionally, ulcers may evolve on the surface of the lumps, what is often an indication of a rather critical tumor. The general condition of the she-dog may even be impaired in case of small tumors; the dog may appear lethargic and tired. Malignant tumors tend to metastasis formation (metastasis - secondary tumors which develop due to migration of viable tumor cells into another place) and proliferate above all into the lymph nodes or into the lung. Other organs may also be affected. The prognosis for malignant tumors of the mammary line is to be considered as rather bad, for benign tumors, however, as rather favorable.


A tumor is considered a degeneration of the body's own cells. Favorable factors for the development of mammary tumors are overweight or the hormonal suppression of heat (with the hormones gestagen and estrogen).


The type of the tumor is determined by examination of an extracted tissue sample. X-ray photographs and other diagnostic measures assist in examining tumors. Tumors on the mammary line shall be treated surgically. The veterinarian normally removes the complete mammary line since removed lumps may often develop again in adjacent regions of the same line. Partly, however, it is sufficient to remove only the neoplasm. Possibly, in extreme cases, both mammary lines need to be removed completely. The best procedure needs to be determined individually for each animal.

Emergency measures

In case you find a lump in the area of the mammary line of your she-dog, you should consult a veterinarian as soon as possible. If your she-dog was not sterilized prior to the first or second heat, you may regularly feel the mammary line for lumps. Your veterinarian will show you how to proceed. The castration of your she-dog prior to the first heat considerably reduces the risk of development of a breast tumor. Also prior to the second heat, the intervention will considerably reduce the risk of the disease. All she-dogs which are sterilized at the end of the second heat, contract breast tumors just as frequently as she-dogs not being sterilized. Please observe that the administration of sex hormones (particularly estrogen and gestagen) for hormonal heat suppression will increase the probability of the appearance of a breast tumor.

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