Animal anatomy, histology, pathological anatomy

3. Tumors- which arise as a result of irregular cell division when they do not obey the body. Tumors can form in all tissues of the body.
Causes. The carcinogenic theory, explained by several theories, is believed to be caused by exposure to harmful substances (alkaloids, waste products). Physicochemical effects can also cause cell division. It has been argued that the dysontogenetic theory is the result of the influence of residual substances left behind after embryonic development.
Structure of tumors. All tumors differ from each other in the structure of the parenchyma. tumor, which consists of two parts - the parenchyma and stroma of all tumors. There are two types of tumor growth. Expansive and infiltrative. Expansive - extensive growth is considered limited to tumor growth, and this growth is observed in benign tumors. Infiltrative growth is characterized by metastases and occurs in malignant tumors.
Types of tumors. Mature and immature.
It is always possible to determine whether the tumors from which they originate are benign or mature tissues. Such tumors do not have a destructive effect on the body; they grow slowly and quickly, in the form of a single primary nodule.
compresses tissue, but does not collapse. However, in some cases, benign tumors can become dangerous. It depends on their location. Safe tumors are easy to remove surgically.
Mature tumors tend to be less dangerous due to differentiated or completely different cell function. Depending on its histological structure, it is sometimes very difficult to determine what tissue the tumor consists of. Tumors with low stroma grow faster, tumors with more stroma grow slower than benign tumors. The most important features of malignant tumors are listed below: infiltration, metastasis, relapse, impact on the general condition of the body.
Tumors that develop from connective tissue include fibromas, myxomas, chondromas, osteomas, and lipomas. Sarcoma is a malignant tumor that develops from connective tissue.
Tumors developing from epithelial tissue are mature - papilloma, adenoma. immature - cancer.Tumors A tumor, or blastoma, is an atypical new tissue formation that differs from other forms of growth (regeneration, hyperplasia, proliferation, metaplasia). A tumor can arise in any tissue, any organ and develop both in humans and in many animals and plants. The existence of malignant neoplasms has been known to mankind since ancient times. Hippocrates and other founders of ancient medicine distinguished tumors from other diseases. Neoplasms have been found in Egyptian mummies. However, until the end of the 19th century, tumors were considered a relatively rare disease. Etiology of tumors. Substances that cause tumor formation are called oncogenic. Agents that cause the formation of malignant tumors are called carcinogenic. Currently, it is customary to consider four groups of causes in oncogenesis: the action of chemical, physical, viral and genetic factors. Chemical oncogenesis. Chemical oncogenesis includes: the action of carcinogenic substances; food oncogenesis; hormonal oncogenesis. One of the main problems associated with the identification of carcinogenic chemicals is the long latent period, which lasts 20 years or more. If a substance does not cause severe consequences immediately, it is difficult to determine the degree of its carcinogenicity due to the huge number of chemicals to which a person is exposed throughout his life. Nutritional oncogenesis. There is evidence of the occurrence of tumors under the influence of foods that are not chemical carcinogens. A diet high in animal fats is statistically associated with an increased incidence of colon and breast cancer; this observation remains unexplained. Hormonal oncogenesis is caused by estrogens, steroid hormones, etc. Physical (radiation) oncogenesis. Many types of radiation can lead to the development of tumors, most likely through a direct effect on DNA or through activation of cellular oncogenes. Ultraviolet radiation: Ultraviolet radiation from the sun plays a role in the development of various types of skin cancer, including squamous cell carcinoma, basal cell carcinoma, and malignant melanoma. X-Rays: After the discovery of X-rays, early radiologists who were exposed to low-penetrating radiation often developed radiation dermatitis, leading to an increased incidence of skin cancer. As the penetrating power of radiation increased, the incidence of leukemia increased among subsequent generations of radiologists. Radioisotopes: The carcinogenic 46 effect of radioactive materials was first identified as a result of an investigation into the causes of a large number of osteosarcomas among workers in a factory where radium-containing paints were used in the production of luminescent dials. Radioactive contamination: Three large groups of people were exposed to radioactive fallout. These are the Japanese in Hiroshima and Nagasaki, Atomic bomb survivors who experienced significant increases in the incidence of leukemia and breast, lung and thyroid cancers. Residents of the Marshall Islands were accidentally exposed to radioactive fallout during an atmospheric nuclear bomb test in the South Pacific. The radioactive fallout was rich in radioactive iodine, which led to the development of multiple thyroid tumors. The Chernobyl nuclear power plant disaster in 1986 also released radioactive iodine into the atmosphere, killing several thousand people. Viral oncogenesis. DNA and RNA viruses can cause neoplasia. Genetic oncogenesis (the role of heredity in oncogenesis). In most cases, genetic predisposition to the development of tumors arises from the inherited loss of one or more tumor suppression genes. Theories of tumor development. Currently, there are two main theories of the occurrence of neoplasms - the theory of monoclonal origin and the theory of “tumor field”. According to the theory of monoclonal origin, the initial carcinogenic agent (tumor-causing factor) causes mutations in a single cell, the division of which then produces a tumor clone that makes up the neoplasm. “Tumor field” theory: a carcinogenic agent, acting on a large number of similar cells, can cause the formation of a field of potentially neoplastic cells. The neoplasm may then develop as a result of the proliferation of one or more cells within this field. To explain the mechanisms of occurrence of both the tumor monoclone and the “tumor field,” a number of other concepts have currently been proposed. Theory of genetic mutations. Disturbances in the genome, caused by heredity, spontaneous mutations, or the action of external agents, can cause neoplasia if growth-regulating genes are damaged. Theory of viral oncogenes. Oncogenic DNA and RNA viruses also contain sequences that function as oncogenes and are inserted directly into the cell genome. Epigenetic theory. According to the epigenetic theory, the main cellular damage occurs not in the genetic apparatus of the cell, but in the mechanism for regulating gene activity, especially in proteins whose synthesis is encoded by growth-regulating genes. Immune surveillance failure theory. According to this theory, neoplastic changes occur quite often in the cells of the body. As a result of DNA damage, neoplastic cells synthesize new molecules (neoantigens, tumor antigens). The body's immune system recognizes these neoantigens as “foreign,” which leads to the activation of a cytotoxic immune response that destroys neoplastic cells. Clinically detectable neoplasms occur only if they are not recognized and destroyed by the immune system. Morphology of tumors. 47 Properties of tumors, distinguishing them from other forms of growth and determining their essence are: organoidity; atypism; infinity of growth; inexpediency relative autonomy; progression. Organoidity. The tumor consists of parenchyma and stroma. Parenchyma is the tumor’s own tissue, constituting its main mass and determining its growth and character. The stroma consists of connective tissue; the vessels and nerves feeding the tumor pass through it. Atypism is a set of biological properties that distinguish newly formed tissue from the original tissue. The acquisition by a tumor cell of new properties not inherent in a normal cell is called anaplasia (from the Greek ana - back, plasis - formation) or cataplasia (from the Greek kata - top to bottom, plasis - formation). The term cataplasia is most accepted in modern literature. There are morphological, functional, antigenic atypism and metabolic atypism (metabolic). Morphological atypia is divided into tissue and cellular. Tissue atypia is characterized by a violation of the size, shape and relationships of tissue structures. Cellular atypia at the light-optical level is expressed in polymorphism of cells, nuclei and nucleoli, polyploidy, changes in the nuclear cytoplasmic index in favor of nuclei, and the appearance of many mitoses. Tumor cells vary in size, shape, and nuclear density. Often the nuclei are large, hyperchromatic, containing several nucleoli, sometimes hypertrophied. Cellular atypia can be expressed to varying degrees. When benign or slow-growing malignant tumors proliferate, neoplastic cells tend to differentiate. Infinity of growth. Cancer cells are “immortal”; they are capable of dividing indefinitely, as many times as they want (normal cells make a maximum of only 30 divisions – the Highflick threshold). Tumor growth stops only as a result of the death of the tumor carrier organism. Excessive cell proliferation: Neoplastic cells may divide more quickly than normal cells. The resulting accumulation of cells in tissues usually takes on a definite shape, but in leukemia the tumor cells are distributed in the bone marrow and blood and do not form a limited mass. Inappropriate. Tumor growth, which does not bring any benefit to the body, but, on the contrary, inhibits all its protective and adaptive systems, is absolutely inappropriate in the Darwinian understanding. Tumor progression. Tumor progression is understood as a persistent, irreversible qualitative change in one or more properties of the tumor. Metastasis is the formation of secondary foci of tumor growth (metastases) as a result of the spread of cells from the primary focus to other tissues. Metastases arise only from malignant neoplasms. Metastasis consists of 4 stages: 1) penetration of tumor cells into the lumen of a blood or lymphatic vessel; 2) transfer of tumor cells by blood or lymph flow; 3) stopping of tumor cells in a new place (metastasis - from 48 Greek meta stateo - otherwise I stand); 4) release of tumor cells into perivascular tissue; 5) growth of metastasis. Tumor recurrence is its reappearance in the same place after surgical removal or radiation treatment. A recurrent tumor develops from remaining tumor cells or an unremoved tumor field. The most dangerous period in terms of recurrence is the first year after tumor removal, then the frequency of recurrence decreases. Tumor growth. There are three types of tumor growth: expansive; infiltrative; appositional. With expansive growth, the tumor grows, pushing away surrounding tissue. The tissues surrounding the tumor atrophy, are replaced by connective tissue, and the tumor is surrounded, as it were, by a capsule (pseudocapsule). Expansive tumor growth is usually slow and is characteristic of mature benign tumors. However, some malignant tumors, such as fibrosarcoma and kidney cancer, can grow expansively. During infiltrative growth, tumor cells grow into surrounding tissues and destroy them. The boundaries of the tumor during infiltrative growth are not clearly defined. Infiltrative tumor growth is usually rapid and is characteristic of immature, malignant tumors. Malignant neoplasms penetrate normal tissue and form outgrowths of neoplastic cells that extend in all directions. Malignant neoplasms usually do not form capsules. Appositional tumor growth occurs due to the neoplastic transformation of normal cells into tumor cells, which is observed in the tumor field. An example of such growth is the desmoids of the anterior abdominal wall. In relation to the lumen of a hollow organ, endophytic and exophytic tumor growth are distinguished. Endophytic growth is the infiltrative growth of a tumor deep into the organ wall. Exophytic growth is the expansive growth of a tumor into an organ cavity. Appearance of the tumor. There are four main types of tumor based on their macroscopic appearance: node; infiltrate; ulcer; cyst. The node is a compact neoplasm with clear boundaries. The node may look like a mushroom cap on a wide stalk, or a polyp. Its surface can be smooth, bumpy or papillary and resemble cauliflower. Infiltrate is a compact neoplasm without clear boundaries. An ulcer is a macroscopic appearance of a tumor in the form of a tissue defect with ridge-like edges, a tuberous bottom and infiltrating growth. A cyst is a neoplasm with clear boundaries and a cavity. The degree of maturity of a tumor cannot be determined by the appearance of a tumor, although, undoubtedly, benign tumors often grow in the form of a node or cyst, and malignant tumors often grow in the form of an infiltrate or ulcer, but there is no strict unambiguous relationship. Tumor size. The size of the tumor can vary from several millimeters to tens of centimeters. Its weight can also be varied - in 49 literature a tumor from adipose tissue - lipoma - weighing more than 100 kg is described. The size of the tumor is determined by its growth rate, duration of existence, and location. The size of the tumor cannot be used to judge the degree of its malignancy. Blood supply to the tumor. The tumor is supplied with blood from the body's bloodstream through pre-existing vessels in the surrounding tissue. In addition, under the influence of a protein substance produced by tumors - angiogenin - a new formation of the capillary network of the tumor stroma occurs. Tumor vessels are also characterized by atypia. Nomenclature of tumors. The name of a benign tumor is in most cases formed by adding the Latin or Greek name of the tissue with the ending -oma. For example, fibroma, papilloma, leiomyoma, adenoma. The name of malignant tumors from epithelial tissue is formed by adding the word carcinoma (cancer, or cancer) to the Latin or Greek name of the tissue. For example, adenocarcinoma, squamous cell carcinoma. For malignant nonepithelial tumors, the second word-forming element is the term sarcoma or blastoma. For example, liposarcoma, ganglioneuroblastoma. Principles of tumor classification. According to the clinical course, all tumors are divided into benign and malignant. Benign tumors are mature, they grow expansively, do not infiltrate the surrounding tissue, forming a pseudocapsule of compressed normal tissue and collagen, tissue atypism predominates in them, and do not metastasize. Malignant tumors are immature, grow infiltratively, cellular atypia predominates, and metastasize. Histogenetic – based on determining whether a tumor belongs to a specific tissue source of development. In accordance with this principle, tumors are distinguished: epithelial tissue; connective tissue; muscle tissue; vessels; melanin-forming tissue; nervous system and meninges; blood systems; teratomas. Histological according to the degree of maturity (according to WHO classifications) - the classification is based on the principle of severity of atypia. Mature tumors are characterized by a predominance of tissue atypism, while immature tumors are characterized by a predominance of cellular atypism. Oncological – according to the International Classification of Diseases. According to the prevalence of the process - the international TNM system, where T (tumor) is the characteristic of the tumor, N (nodus) is the presence of metastases in the lymph nodes, M (metastasis) is the presence of distant metastases. 9.2. Leukemia Systemic diseases of hematopoietic tissue, characterized by tumor-like proliferation of its cells. Unlike other tumors, cell proliferation begins simultaneously in many hematopoietic organs and sites of potential hematopoiesis. 50 Lymphoid leukemia. A typical picture is observed in cattle and is more common than others. At autopsy, the lymph nodes are enlarged to several kilograms, the parenchyma is white-gray, flabby, with necrosis and hemorrhages. The spleen is enlarged, the capsule is tense, sometimes ruptures, with hemorrhages and necrosis. The follicles are greatly enlarged, with foci of leukemic growths. The liver and kidneys are enlarged, riddled with gray-red nodules and cords. In the bone marrow and various internal organs, proliferation of lymphoid tissue. On histological examination, the newly formed tissue consists of lymphocytes, prolymphocytes and rarely lymphoblasts. On average, the nuclear sizes of leukemia cells are larger than those of normal cells. The nuclei are often in a state of peknosis and lysis. Myeloid leukemia is uncommon and is characterized by severe bone marrow hyperplasia. Yellow bone marrow turns into red, in the lymph nodes, spleen, liver, kidneys and other organs there are new foci of hematopoiesis. In myeloid leukemia, the newly formed cells resemble myeloblasts, myelocytes. Myeloblasts have a large nucleus with a wide rim of non-granular cytoplasm. Myelocytes have a round nucleus and granular cytoplasm. Avian leukemia is characterized by damage mainly to internal organs. Tumor nodes or white-gray infiltrates are found in the skin, muscles and bones. The liver, kidneys, and spleen are enlarged, lumpy or with numerous nodules of a sarcomatous appearance. There are lymphoid, myeloid and erythroid leukemias. Questions for self-control 1. Etiology of tumors. 2. Theories of tumor development. 3. Morphology of tumors. 4. Principles of tumor classification. 5. Lymphoid leukemia. 6. Myeloid leukemia.