Cancer (cancer, carcinoma is a malignant tumor of epithelial tissue. For cancer and other malignant tumors characteristic: invasiveness (germination, implementation nearby tissue and organs), the ability to form metastases (see), the tendency to relapse after removal, the ability to cause cachexia (see). If the action is different, not always found etiological (causal) factors in normal epithelial tissue lesions appear modified cells that can grow fast and are different from the parent anatomical changes of the structure and biological properties; acquire at this relative independence from the differing growth of tissues in normal conditions. Tumor cells form large concentrations, are introduced into the surrounding tissues, destroy them. The mechanism of action of carcinogenic substances (see) on normal epithelial tissue is not fully studied, and are carcinogenic factors that all is not well known. Differences in structure of the cancer cells from normal cells of the epithelium can be detected by microscopic examination.
The cancer tissue under a microscope appears to be less differentiated, i.e., the partial or complete lack of distinctive (differential) signs of normal cells of this body and its structure as a whole.
Cancer can develop wherever there epithelial tissue- of skin cancer, gastrointestinal, genitourinary tract, etc.
The spread (metastasis) of cancer cells occurs mainly on the flow of lymph, so cancer metastases usually primarily formed in the nearest regional lymph nodes, which are flowing lymph from this body. Relapses after operations occur not only in the case of incomplete removal of the tumor (so-called direct recurrence), but if there are imperceptible to the eye cancerous changes in tissues outside of the surgical field. Finally, the cause of relapse may be a violation of ablation (see), leading to the ingress of cancer cells in the tissue of the surgical field. Cachexia associated with intoxication due to breakdown and infection of the tumor, with constant bleeding from her; development of cachexia is accelerated by the cancer location in vital organs, leading to depletion of the patient from starvation (cancer of the esophagus, stomach, liver, pancreas, etc., When some localizations of a cancer (cancer of the lung, colon, breast, thyroid gland, uterus) cachexia can not happen soon, to be poorly expressed or long be absent.
Cancer of hollow organs grows or ekzotichna, i.e. in the clearance authority (mushroom, polypoid cancers of the stomach, colon, cervix and other), or endofitno, infiltrating the walls of the body and penetrating through them into the surrounding tissue.
Depending on the degree of development in the tumor connective tissue (stroma) distinguish poor stroma cancer (medullary, a brain) and serosny cancer, rich dense stroma with a small number of cancer cells, often less current malignant. The most differentiated form of glandular cancer is a malignant adenoma, less differentiated - adenocarcinoma; it consists of polymorphic ferrous tubes, randomly laid in stroma. The least differentiated cylindricity cancer; it is dominated by sharply atypical cells, completely lost resemblance with the original cloth. Squamous cell cancers can be built from less differentiated, non-squamous, or a more differentiated, orogovevshi cells with the formation of the so-called cancer "gems".
Methods of cancer diagnosis varied and depend on its location; most reliable method is to biopsy (see) with histological examination suspicious for cancer cloth. Diagnosis of cancer has improved with the use of modern methods of research: endoscopy (cancer of the esophagus, bronchus, stomach, and others), puncture biopsy, taking smears from the surface of the tumor. Cytological examination of the received material allows to distinguish cancer cells from normal cells and between cells in inflammatory exudates. A special place in the diagnosis of cancer is x-ray examination, which in many cases reveals cancer of the esophagus, stomach, intestine, lung, and it could be supplemented layered images (tomography) or application of electronic-optical amplifier in the study of the gastrointestinal tract. In the early stages of clinical symptoms of cancer are often unclear, uncommon, scarce. In the later stages of cancer symptoms much clearer, more likely to experience pain syndromes appear weight loss, fatigue, appetite changes.
The growth rate of cancer is diverse: the latent period of the flow of some forms of cancer can last several years, for example in peripheral lung cancer. For cancer depends not only on the extent of its distribution in the body, but also from a number of other conditions. Indeed, the rapid growth of cancer often occurs at a young age; during pregnancy or lactation growth of cancer or its metastases may also accelerate.
Cancer treatment is closely associated with the concept of clinical stages. Adopted in the USSR classification cancer involves dividing it into 4 stages.
The first stage is characterized by small size of the tumor, which does not exceed the limits of this body and metastasized; the second stage is more common tumor, often with the transition to nearby tissue or nearest lymph nodes; the third stage is characterized by the extensive spread of tumors to adjacent tissues and organs and the presence of multiple regional metastases; fourth stage - extensive tumor spread far beyond the affected organ with many distant metastases.
New international classification of tumors includes evaluating three indicators: 1) the size of the primary tumor, denoted by the letter T (tumor); 2) the status of regional lymph nodes, denoted by the symbol N (nodi); 3) the presence of distant metastases, designated by the letter M (metastasis). International system of "TNM" can give a full description of the stage of neoplastic process using additional digital designations under the above letters; for example, T2N1M0 means the cancer is the second stage with regional lymph nodes, but without distant metastases. The most favorable long-term results of treatment of cancer observed in the first and second stages of the disease. Cm. also the Tumor, anti-cancer drugs.