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Tumors in cats and dogs: causes and types


Tumors or neoplasms are called local excess, autonomous, atypical pathological growths of one or several body tissues that arise for no apparent reason due to the multiplication of cellular elements caused by changes in the biological properties of cells under the influence of blastomogenic factors of the external and internal environment. The doctrine of tumors or neoplasms is allocated in an independent department of science called oncology. The basis of tumor growth is the unlimited reproduction of cells, which is not coordinated with the growth of other body tissues and continues after the elimination of the causes (carcinogens, x-rays and radioactive radiation, injuries, etc.) that caused their appearance. Tumor cells are formed from normal cells of any organs and tissues of the body. Unlike normal cells, they acquire new special hereditary morphological and functional properties. Consequently, autonomy and independence of growth (autonomous growth) and primary atypical morphological and physiological deviations of cellular elements from the type of mother cells are the main characteristic signs of tumors. Etiology. Many different theories of blastomogenesis have been proposed. However, the causes of tumors have not yet been elucidated. Until recent years, two theories of their origin were most common: the theory of embryonic embryos of Conheim and the theory of chronic irritation of Virchow. These, as well as other theories, trying to find a single cause for all types of tumors, have not received convincing evidence. Theory of Conheim (dysontogenetic theory 0 reduces the origin of tumors to proliferation of excess, unspent during embryonic life, disconnected from normal communication, or “lost” germinal buds. While other cells of this embryonic organism undergo division and turn into normal tissues and organs, cell groups in the germinal buds remain dormant - dormant, these rudiments can be found among histologically related tissues, as well as undergo movement When the embryo reaches its full development, the split off embryonic primordium can remain completely latent and not manifest itself in anything, but they retain in themselves in a potential form all the unspent high energy of growth, which can manifest itself at any moment under the influence of one or another causes (external irritation or internal disturbance of intercellular balance) .Then the cells multiply and produce young, embryonic, less differentiated (than normal tissue cells) cellular e ementy, the sum of which is evolving opuhol.teoriya Kongeyma not explained, however, all the phenomena observed in tumors, especially in malignant tumors, but mostly the appearance of tumors in middle and old age. In accordance with Virchow's theory of irritation (Irritational theory) the cause of many tumors, especially cancer, is the chronic effect on the tissue of physico-chemical stimuli - various types of injuries, exposure to ionizing radiation and solar energy, chemicals of inorganic, organic and biological origin. This theory is well illustrated by professional cancer in humans and animals. For example, skin cancer in oxen around the horns at the point of attachment of the rope, in horses - cancer of the corners of the mouth as a result of trauma to their iron bits, skin cancer in radiologists, lung cancer in workers in cobalt mines, skin cancer in workers in the paraffin industry and working with tar. The transformation of stomach, intestinal, and skin ulcers into a cancerous tumor is also causally associated with chronic irritation. The practical significance of this theory lies in the fact that it makes it possible to prevent the occurrence of certain tumors, but it does not explain the mechanism of the transition of normal cells to tumor cells, the development of a cancerous tumor in those cases when its appearance is not preceded by either chronic inflammation or the influence of external stimuli, but also the problem of congenital tumors and the entire group of benign neoplasms. Parasitic theory of blastomogenesis based on the coincidence of the occurrence of tumors with the presence of certain parasites in the tissues of animals and humans: in cattle - liver cancer with fascioliasis, in dogs and cats - with opisthorchiasis, in gray rats when feeding black cockroaches they develop cancer of the tongue and stomach. But in many cases, this theory of parasites has not been experimentally proven. An interesting theory of the etiology of tumors is viral. The idea that tumors can be caused by agents of a viral nature was first expressed in 1903, and experimentally confirmed in 1908, establishing the viral etiology of leukemia and chicken sarcoma. For a long time, it was believed that tumor viruses are agents that induce the cells affected by them to unlimited and unregulated reproduction. However, Zilber (1968) expressed a different opinion about tumor viruses, according to which, firstly, they hereditarily turn a normal cell into a tumor one, secondly, they do not play a role in the further reproduction of already existing tumor cells, and thirdly, their effect is fundamentally different from an infectious virus. Experimental data and clinical observations show that in some cases a decisive role in the occurrence and development of tumors is hormonal factor. Thus, prolonged administration of estrogen to mice caused the development of breast cancer in both females and males. Ovariectomy in highly developed mouse mice significantly reduces the incidence of breast cancer. Polyetiological theory not trying to reduce the entire variety of tumors to any one reason for their occurrence. Any factors - physical, chemical, biological and others, acting on the genetic apparatus of the cell, cause a mutation - the transformation of normal cellular elements into tumor ones. Classification of tumors. Tumors are classified according to morphological characteristics according to the tissues from which they develop. In accordance with this distinguish: epithelial - papillomas, adenomas, cystomas, dermatomas, carcinomas,connective tissue - fibromas, myxomas, lipomas, chondromas, osteomas, melanosarcomas, vascular - hemangiomas, lymphangiomas,muscle - fibroids, rhabdomyomas, from nerve tissue - gliomas, neuromas, mixed - osteosarcoma, fibromyxochondroma, fibrochondroosteoma. According to the nature of growth and clinical course, tumors are divided into benign and malignant. Benign tumors. They grow slowly, are more often surrounded by a capsule, do not grow into adjacent tissues, and push them apart - expansive growth. Depending on the localization, such a tumor can exist throughout the patient’s life, without causing particular harm. In other rays, a benign tumor during its growth exerts pressure on the adjacent organ, causing atrophy, compression of blood vessels and nerves and disrupting its function. Benign tumors do not ulcerate, do not give metastases and do not cause a general reaction from the body. Metabolism, blood composition and general condition of the animal remain unchanged. After removal of a benign tumor, complete recovery occurs. Malignant tumors. They consist of cells that have undergone irreversible pathological changes and cause constant, progressive intensive growth of tissues consisting of these cells. In this case, all daughter cells of the tumor are also changed. A characteristic feature of malignant tumor cells is deep morphological abnormalities: polymorphism of cells and their nuclei, multinucleation, undifferentiation, abundance of mitoses, etc. Malignant tumors do not have capsules and are characterized by rapid infiltrating growth, destroying neighboring tissues, germinate in them. They are easily ulcerated. However, it should be noted that in animals, the phenomena of infiltrating growth do not always occur. In some cases, malignant tumors have pronounced boundaries and are easily husked upon surgical removal. The cells of malignant tumors, growing into the lymphatic and blood vessels, can break off and be transferred to other organs and tissues by the flow of blood and lymph, causing the development of new tumors - metastases, which is the second feature of malignant tumors. The development of malignant tumors is accompanied by profound metabolic disorders in the animal’s body, causing a deterioration in general condition, sharp exhaustion and degeneration. After surgical removal, malignant tumors often recur with stronger infiltration growth, give regional and distant metastases. Diagnostics.It is rather difficult to establish the presence of a tumor in animals. True tumors should be distinguished from the swelling that occurs with cysts, goiter, hematomas, hernias, dropsy, and various inflammatory processes. It is even more difficult to solve the question of the nature of the neoplasm (benign or malignant). Of the clinical research methods, examination, palpation, percussion, auscultation, radiography and fluoroscopy are used. To determine the type of tumor, its malignancy, a biopsy is used, i.e., microscopic examination of tumor pieces obtained by surgery. In small animals, by the method of bimanual palpation, it is possible to determine the presence of tumors of the abdominal organs. In large animals, rectal examination can detect tumors of the uterus, ovaries and vagina. The most accurate methods for diagnosing neoplasms in determining the nature of the tumor are histological and cytological studies of biopsy tissue and smears prepared from material from the surface of the tumor. Highly sensitive methods of radioisotope and ultrasound diagnostics of tumors have been developed, which are widely used in medical practice. Treatment.As a rule, operational. In the case of malignant tumors is not always advisable.

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What is a tumor?

A tumor, or neoplasm, is called a pathological proliferation of tissues associated with intensive cell division of the body under the influence of various factors.

The problem of neoplasms is becoming increasingly urgent, since cases of their occurrence in both humans and animals have become more frequent.

In this article, we will talk about the causes of tumors in cats and dogs, about malignant and benign neoplasms, about their types, about the latest methods of treating tumors and preventive measures that will help owners protect their pet from this dangerous disease.

Causes of tumor development in cats and dogs

Physical, chemical and biological factors that provoke the appearance of neoplasms are distinguished.

Causes of the development of tumors:

  • Repeated mechanical damage,
  • Exposure to chemicals
  • Irradiation
  • Virus infection
  • Parasite infection
  • Genetic predisposition
  • Hormonal disbalance,
  • Decreased immunity.

Acting individually or in combination, these factors affect healthy cells in the body and cause them to divide uncontrollably. As a result, a tumor develops.

Substances that contribute to the transformation of a benign tumor into a malignant one are called carcinogens, and the conversion process itself is called carcinogenesis.


Preserve the structure of the fabric from which they grew. They have a capsule and do not grow into healthy tissues, but push them apart, Growth

Usually they grow slowly, growth may stop, sometimes the tumor develops back, metastases

Do not give metastases, treatment

Well treated surgically.


Tumor cells are reborn, they are characterized by a simplification of the structure and a loss of differentiation. Growth

They grow quickly, do not have capsules and germinate in the surrounding tissue, metastases

They give metastases, that is, cancer cells break away from the tumor and spread throughout the body with a stream of blood or lymph. Treatment

If untreated, the cancerous tumor leads to the death of the animal. After surgical removal, additional use of drugs and methods that suppress its growth is required.

A benign tumor is not as dangerous as a malignant neoplasm, but it can cause irreparable harm to the body. This especially depends on the location of the tumor and on the intensity of its growth.

Lipomas (adipose)

Lipoma is formed from adipose tissue cells. The tumor has an oval shape and soft consistency. It is limited by the capsule and mobile. Fat dogs and cats usually appear on the stomach, chest, legs, sometimes on the internal organs. With strong growth, they can squeeze adjacent tissues and be painful for the pet. Only surgical treatment is used to remove them.

Chondromas and osteomas

Chondromas and osteomas are formed from cells of cartilage or bone tissue. The spine, joints, some organs are affected. Tumors grow slowly, often they are plural. They represent a danger, as they can degenerate into malignant neoplasms. After removal, often lead to dysfunction of the affected organ.

The tumor consists of muscle fibers. Myoma develops in the uterus, vagina, esophagus, stomach, intestines, bladder, kidney. During treatment, the neoplasm is removed along with the surrounding healthy tissue or the entire organ.

Consist of connective tissue covered with skin or mucous membrane. They develop on the lips, mucous membranes of the oral cavity and nose, eyelids, on the mammary glands, and the penis in animals. Papillomas are single and multiple, of different sizes and shapes, often bleed, can degenerate into malignant tumors. It is proved that viruses cause their formation. In different species of animals, the virus that causes papilloma is unique. In the treatment of papillomas, novocaine is removed, cauterized, or injected.

Skin Cancer in Cats and Dogs

A tumor develops from skin epithelial cells. Elderly pets and animals exposed to radiation are susceptible to skin cancer. The disease begins with the appearance of a small spot on the skin, which does not cause the animal any anxiety. Over time, the tumor begins to grow, itch, itch. The pet licks the hair, then in the middle of the neoplasm, an ulcer appears that bleeds and crusts.

The cancerous tumor grows relatively slowly and is not prone to the appearance of metastases. It may not manifest itself for a long time, so the animal gets to the doctor already in the late stages of the disease, when difficulties arise with treatment.

Mammary cancer

Breast cancer is common in both cats and dogs. The disease develops from breast epithelial cells. Adult animals are subject to it.Breast cancer often leads to the death of a pet, because it gives metastases to other organs: lungs, liver, kidneys.

Four stages of breast cancer are distinguished. First, small dense nodules or one node on one or more mammary glands are formed. Over time, these nodules increase in size, involving neighboring healthy tissues in the process. Tumor cells with a flow of lymph and blood enter the lymph nodes, causing inflammation in them. Then the cancer cells are carried to other organs, where they form new lesion sites.

The prognosis of the disease is favorable in the initial stages. It is treated by removing the entire row of mammary glands on which a tumor is detected.


Osteosarcoma is a malignant bone tumor in cats and dogs that usually develops in animals over the age of 6 years. Osteosarcoma affects the limbs of an animal. Painful swelling and edema appear at the site of tumor localization. Often the mobility of the joint is impaired, a limb fracture develops at the site of the neoplasm.

Osteosarcoma is more often registered in dogs of large breeds: Great Danes, St. Bernards, Dobermans, Shepherds, Retriever. Also, a tumor can provoke various injuries to the limbs.

The main sign of osteogenic sarcoma is the lameness of the animal, unwillingness to get up, pain on palpation, edema.

Surgical treatment followed by chemotherapy. Most often, the entire limb in which the tumor formed is amputated. The prognosis is cautious because osteosarcoma almost always gives metastases.

Pet tumor: what to do?

Did you find a tumor in your pet? Contact a specialist immediately. The main thing to remember: the smaller the tumor in size, the more successful the treatment will be. Do not despair, even if your pet has a cancerous tumor. Modern veterinary oncology does not stand still, new methods of treating malignant neoplasms in animals have been developed.

Chemotherapy and surgical treatment of a malignant tumor

The treatment of tumors is almost always operative or operative in combination with the use of chemotherapy, radiation therapy, immunotherapy. The main task of the oncologist surgeon is the complete removal of the malignant neoplasm. If the tumor is localized, then the surgery is successful and the prognosis for the animal is favorable.

If the animal has multiple tumors and metastases, chemotherapy is used for treatment. The choice of drug will depend on the sensitivity of the tumor and its location. Sometimes the drug is injected into the affected tissue itself.

In the late stages of malignant neoplasms, the complete cure of the animal is often impossible. Then doctors conduct therapy in order to reduce the growth rate of the tumor, minimize the suffering of the animal and increase its quality of life.

Tumor development prevention: how to protect a pet

A tumor in a pet is a disease that must always be remembered and due attention should be paid to prevention:

  • Regularly check your pet for tumors,
  • Visit your veterinarian for a preventive check-up,
  • Provide good nutrition with quality feed,

Causes of Tumors

There are many theories of the appearance of tumors, however, a single cause of origin for all types of tumors has not yet been found.

All theories can be combined into three large groups:

  • Physicochemical theories explain the occurrence of tumors by exposure to carcinogens of a chemical or physical nature,
  • Viral theories of the etiology of tumors claim that all tumors are caused by agents of a viral nature, and carcinogens only create favorable conditions for their exposure,
  • The polyetiological theory - the theory of the multiplicity of reasons, unites all the above theories.

What are the tumors?

There are several principles for the classification of tumors - clinical, morphological, histological, histogenetic, oncological, etc.

According to the clinical course and nature of tumor growth, they are divided into:

Benign tumors grow slowly, do not grow into the surrounding tissue and push them apart, the so-called expansive growth, often surrounded by a capsule.

Depending on the location, such a tumor can exist throughout the life of the animal either without causing particular harm, or if it puts pressure on the adjacent organ and impairs its function, it can lead to serious consequences up to the death of the animal.

Benign tumors do not ulcerate, do not give metastases and do not cause a general reaction from the body.

Benign tumors do not recur, and after removal of such a tumor, complete recovery occurs.

But it is possible degeneration (malignancy) of a benign tumor into a malignant one.

Malignant tumors are characterized by rapid growth, consist of cells that underwent irreversible pathological changes, do not have capsules, often grow into surrounding tissues and destroy them (infiltrating growth). These tumors easily ulcerate.

Malignant tumors are prone to metastasis.

Metastases - These are new growth foci as a result of the transfer of tumor cells through the blood and lymph vessels.

The longer and faster the main tumor grows, the greater the chances of the appearance of metastases. Tumor injury also increases the risk of metastases.

The effect of the tumor on the body

The development of a malignant tumor has a negative systemic effect on the body that is not directly related to damage to organs and tissues by the tumor itself or its metastases. Under the influence of tumor toxins, absorption of its decay products, and secondary infection, deep metabolic disorders occur leading to a deterioration in the general condition of the animal, exhaustion, weakness, anemia, and a decrease in immunity.

Establishing diagnosis

For the diagnosis, a variety of methods are used, such as - taking an anamnesis, examination, clinical and biochemical blood tests, ultrasound, x-ray studies and others. The choice of diagnostic method depends on the individual characteristics of the patient and the course of the disease.

In most cases, for differential diagnosis, it is necessary to conduct several studies, combining various methods. A biopsy is often required to evaluate tissue and tumor cells using cytological and histological studies.

The use of various diagnostic methods allows you to obtain the most complete information about the course and stage of the tumor process and to develop the optimal treatment regimen.

Treatment and prevention

The most important factor in the treatment of oncology is time - the vast majority of tumors can be cured if treatment is started on time.

In modern veterinary medicine, a number of effective methods are used to treat tumors - surgical, chemotherapeutic, immunotherapy, radiation, hormonal, biotherapy, as well as a combination of several of these methods.

At this stage, the main treatment for neoplasms is surgical removal. The effectiveness of surgery depends on the stage of tumor development, the degree of germination of the tumor in the surrounding tissue, the presence of metastases.

The sooner you contact a specialist, and the sooner an accurate diagnosis is made, the more chances there are for a complete cure of the animal.

The best prophylaxis of metastases is the earliest and minimally traumatic removal of the tumor.

In any case, even in a neglected case, it is worth showing the pet to the doctor, since even if it is impossible to completely cure, you can significantly extend the animal’s comfortable life.