Precancer – group of the congenital and acquired pathological states preceding development of oncological defeat but which not always are transformed to a malignant tumor. Can be facultative or obligate. The group of precancers includes a large number of diseases of inflammatory, not inflammatory and dystrophic character, malformations, age changes and good-quality a neoplasia. It is diagnosed on the basis of clinical, laboratory and tool trials. Tactics of treatment and a measure of prevention of an ozlokachestvleniye are defined by a look and localization of pathological process.
Precancer – the changes of bodies and fabrics which are followed by increase in probability of development of malignant new growths. Their existence does not mean obligatory transformation in cancer, the malignization is observed at only 0,5-1% of the patients suffering from various forms of a precancer. The foundation was laid for a research of this group of diseases in 1896 when the dermatologist Dyubreyl suggested to consider keratoza as the pathological states preceding skin cancer. In the subsequent the theory of precancers became a subject of researches of doctors of various specialties that led to formation of the integral concept considering clinical, genetic and morphological aspects of formation of cancer tumors.
The modern version of this concept is based on the idea that malignant the neoplasia practically never arises against the background of healthy fabrics. For each type of cancer there is the precancer. In the course of transformation from healthy fabric to a malignant tumor of a cage there pass certain intermediate stages, and these stages can be allocated when studying morphological structure of an affected area. Scientists managed to define precancers for many crayfish of various localization. At the same time, predecessors of other groups of oncological defeats so far in most cases remain not established. Treatment of pretumoral processes is performed by experts in the sphere of oncology, dermatology, gastroenterology, pulmonology, gynecology, a mammology and other fields of medicine.
Classification of precancers
Distinguish two types of precancers: facultative (with low probability of a malignization) and obligate (regenerating in cancer in the absence of treatment). Experts consider these pathological processes as two initial stages of a morphogenesis of cancer. The third stage is noninvasive cancer (carcinoma in situ), the fourth – early invasive cancer. The third and fourth stage are considered as the initial stages of development of a malignant new growth and do not join in group of precancers.
Taking into account localizations allocate the following types of precancers:
- Skin precancers: Pedzhet's disease, Bowen, a pigmentary xeroderma, a skin horn, senile , beam dermatitis, it is long the existing fistulas, post-traumatic and trophic ulcers, postburn hems, damages of skin at hard currency, syphilis and tuberculosis, congenital malformations and acquired diseases of skin.
- Precancers of a red border of lips: , papillomas.
- Precancers of a mucous oral cavity: cracks, ulcers, .
- Precancers of a nasopharynx and throat: papillomas, diskeratoza, basal , hondroma, adenoma, contact fibroma.
- Precancers of a mammary gland: knotty and diffusion disgormonalny giperplaziya.
- Precancers of female genitals: giperkeratoza, erosion and polyps of a neck of a uterus, endometrium giperplaziya, endometrium polyps, adenomatosis, puzyrny drift, some kistoma of ovaries.
- GIT precancers: postburn hems of a gullet, gullet leukoplakia, gastritis, stomach ulcer, adenomatozny polyps of a gullet, stomach and intestines, ulcer colitis, fistulas and cracks of back pass, hems of various localization.
- Precancers of a liver and biliary tract: cirrhosis, cholelithiasis, gepatoma.
- Precancers of urinary tract, testicles and prostate: a leukoplakia mucous a bladder, papilloma, adenomas, a kriptorkhizm, a prostate gland giperplaziya, teratoidny tumors of a small egg, specific defeats of an appendage of a small egg at gonorrhea and tuberculosis.
Facultative precancers are chronic diseases and states with rather low risk of a malignization. Such pathological processes are followed by dystrophy and an atrophy of fabrics, and also violation of processes of cellular regeneration with formation of sites of a giperplaziya and metaplaziya of cages which in the subsequent can become a source of a malignant tumor. Include chronic nonspecific and specific inflammatory processes in group of facultative precancers, including – ezofagit, atrophic gastritis, stomach ulcer, ulcer colitis, an erosion of a neck of a uterus and many other diseases. Besides, in this group refer some anomalies of development, age changes and good-quality a neoplasia.
Obligate precancers are considered as pathological states which in the absence of treatment are transformed to cancer sooner or later. The probability of a malignization at such defeats is higher, than at facultative precancers. The majority of obligate precancers is caused by hereditary factors. Carry adenomatozny polyps of a stomach, Bowen's dermatosis, a pigmentary xeroderma to number of such diseases, family polyposes of a large intestine etc. Feature of obligate precancers is the dysplasia which is characterized by change of a form and appearance of cages (a cellular atipiya), violation of process of a differentiation of cages (formation of cages of various level of a maturity with prevalence of less specialized forms) and violation of very tectonics of fabrics (change of normal structure, emergence of sites of asymmetry, atypical interposition of cages etc.).
Experts usually allocate three degrees of a dysplasia at a precancer: weak, moderate and expressed. The main criterion defining dysplasia degree is the level of an atipiya of cages. Progressing of a dysplasia is followed by increase of cellular polymorphism, increase in kernels, emergence of a giperkhromnost and increase in quantity of mitoses. Emergence of sites of a dysplasia at a precancer not necessarily comes to the end with formation of a clone of malignant cages. Process stabilization, reduction or increase in expressiveness of pathological changes are possible. Than stronger the dysplasia is expressed – the probability of a malignization is higher.
Pretumoral states (precancers)
Precancer diseases of skin are the widespread and well studied group of precancers. The leading place in the list of the factors provoking such pathological states is occupied by adverse meteorological effects, first of all – excess insolation. Besides, the increased humidity, wind and low ambient temperature matter. Precancers of skin can be provoked by long contact with chemical carcinogens, including – tar, arsenic and lubricants. Beam dermatitis arises when receiving a high dose of ionizing radiation. Blood supply violations become the cause of trophic ulcers. Post-traumatic ulcers can be formed on the place of extensive purulent wounds. In development of some diseases an important role is played by adverse heredity.
The risk of a malignization of a keratoakantoma makes about 18%, a skin horn – from 12 to 20%, postburn damages of skin – 5-6%. The diagnosis of a precancer of skin is exposed taking into account data of the anamnesis and external survey. If necessary carry out a material intake for a cytologic research. Treatment usually consists in excision of the changed fabrics. Expeditious removal, cryodestruction, laser therapy, a diatermokoagulyation are possible. At some precancers therapy of the main disease, bandaging, skin plasticity etc. are required. Prevention consists in minimization of harmful effects, observance of safety regulations during the work with chemical carcinogens, timely adequate treatment of traumatic damages and inflammatory diseases of skin. Patients from risk group have to look round regularly the dermatologist.
Carry a large number of chronic diseases of digestive tract to precancers of a GIT. Atrophic gastritis, opukholstimuliruyushchy gastritis (Monetriye's disease), stomach ulcer of a stomach, adenomatozny polyps of a stomach and intestines, a disease Krone and nonspecific ulcer colitis have the greatest value. The reasons of development of precancers can differ. Important factors are adverse heredity, infection of Helicobacter pylori, violation of the food mode (irregular meal, the use sharp, fat, fried) and autoimmune violations.
The probability of a malignization of precancers of a GIT significantly differs. At family to a polypose of a thick gut the ozlokachestvleniye is observed in 100% of cases, at large adenomatozny polyps of a stomach – in 75% of cases, at Monetriye's disease – in 8-40% of cases, at atrophic gastritis – in 13% of cases. At stomach ulcer of a stomach the forecast depends on the size and an arrangement of an ulcer. Large ulcers malignizirutsya more often than small. At defeat of big curvature (very rare localization of an ulcer) malignant regeneration is noted at 100% of patients.
The leading role at diagnosis is usually played by endoscopic methods of a research. When carrying out gastroscopy and kolonoskopiya the doctor estimates the size, localization and the nature of a precancer and carries out an endoscopic biopsy. Tactics of treatment is defined by a type of pathological process. To patients appoint a special diet, carry out conservative therapy. At high risk of a malignization carry out surgical excision of precancers. Preventive measures include observance of a diet, timely treatment of aggravations, correction of immune violations, early identification of persons with hereditary predisposition, regular surveys of the gastroenterologist in combination with tool researches.
Precancers of female reproductive system
Experts unite precancers of female genitals and mammary glands in group of precancer diseases of female reproductive system. Among risk factors of development of precancers researchers specify adverse heredity, age exchange and endocrine frustration, early sexual activity, numerous childbirth and abortions, lack of childbirth, venereal diseases, some viral infections (a virus of papilloma of the person, a herpes virus 2 types), smoking, use of chemical contraceptives and professional harm.
When diagnosing a precancer consider data of gynecologic survey, a kolposkopiya, hysteroscopy, ultrasonography of bodies of a small pelvis, Schiller test, researches of scrapes of a neck of a uterus, mammography, a histologic research and other techniques. Treatment can include a diet, physiotherapy, hormonal medicines, protivozudny and antimicrobic means etc. For removal of different types of a precancer chemical coagulation, a diatermokoagulyation, radio destruction, cryosurgery and traditional surgical techniques are used. Indications to operation and the volume of intervention are defined individually with the anamnesis of a disease, risk of malignant transformation, age of the patient and other factors.