What is a precancer?

The morphogenesis of tumors, or the mechanism of their development in morphological illumination, can be divided into a precancer and the stage of tumor formation and growth.

A pre-cancer is a change in an organ or tissue that passes into cancer with a greater degree of probability than in immutable organs or tissues. However, the presence of a background such as a precancer does not yet indicate that it will turn into cancer. Malignancy in precancer is observed in 0.1-5.0% of cases. The identification of such changes is not only theoretical, but also of great practical importance. It allows to allocate groups of the raised risk concerning possibility of development of a tumor of this or that organ, to prevent occurrence of a tumor and to diagnose it as soon as possible.

Among the precancer, morphologists distinguish so-called background changes, manifested by dystrophy and atrophy, hyperplasia and metaplasia. This includes almost all chronic inflammatory specific and nonspecific processes. For example, in the stomach - a chronic gastritis of various etiologies; in the lungs - chronic bronchitis; in the liver - chronic hepatitis and cirrhosis; in the mammary gland - mastopathy; in the cervix uteri - erosion and leukoplakia; in the thyroid gland - diffuse and nodal goiter, etc.

These changes, leading to structural rearrangement of organs and tissues, become the basis for the emergence of foci of hyperplasia and dysplasia, which are considered as a proper pre-cancer.

The most important among the precancer is recently given to cell dysplasia (from the Greek dys - impairment and ptosis - formation), which always appears in the bowels of the disregenerator process and is accompanied by insufficient and incomplete differentiation of stem tissue elements, impaired coordination between proliferation and cell maturation processes.

Depending on the severity of nuclear and cellular atypia, a three-degree gradation of dysplasia is most often used: mild (D1), moderately expressed (D2) and severe (DZ). The determining criterion for the degree of dysplasia is the severity of cellular atypia. As the degree of dysplasia increases, there is an increase in the size of the nuclei, their polymorphism, hyperchromia, coarsening and lumpiness of chromatin, an increase in the number and relative size of the nucleoli, and an increase in mitotic activity. Over time, dysplasia can regress, be stable or progress. A weak degree of dysplasia has little to do with cancer, and the reverse development of mild and moderate dysplasia is everywhere. The more pronounced dysplasia, the less likely it is to reverse its development. The possibility of the transition of dysplasia into cancer in situ and, consequently, in cancer increases with the increase of its severity. Proceeding from the fact that some precancerous conditions necessarily pass into cancer, while others do not pass, they are subdivided into an obligate and facultative pre-cancer.

Obligatny predrak, i.e. The pre-cancer, necessarily culminating in the development of cancer, is more often associated with a hereditary predisposition. This congenital polyposis of the large intestine, pigmentary xeroderma, neurofibromatosis (Recklinghausen's disease), retinal neuroblastoma, etc. The precarious precancer requires mandatory complex of preventive measures and even radical treatment, and patients on the obligate precancer should be registered with an oncologist.

An optional precancer is this hyperplastic-dysplastic process, as well as some dysembryoplasia.

The so-called latent period of cancer, i.e. The period of existence of the precancer to the development of cancer, for tumors of different localization is different and is estimated for years (up to 30-40 years). The term "latent period of cancer" is applicable only to obligate precancer.

Thus, with early oncological pathology, four consecutive phases of cancer morphogenesis can be distinguished: I - precancerous states - facultative precancer; II - precancerous conditions - obligate precancer; III - pre-invasive cancer - carcinoma in situ and IV - early invasive cancer.

The formation of a tumor, or the transition of precancerous changes to cancer, has been studied insufficiently. Based on the experimental data, the following tumor development scheme can be assumed:

• violation of the regenerative process;
• premature changes characterized by hyperplasia and dysplasia;
• the resulting stage malignant proliferating cells;
• the appearance of a tumor rudiment;
• progression of the tumor.

Recently, the theory of the "tumor field" that reveals the stage-by-stage nature of tumor development has become widespread. According to this theory, multiple points of growth appear in the organ - focal proliferates, which constitute a "tumor field". Moreover, the malignant transformation (malignancy) of focal proliferates occurs consistently from the center to the periphery until the focalization of malignancy fuses into one tumor node; however, primary-multiple growth is possible. After the "tumor field is spent", the tumor grows "on its own", it should be noted the controversial nature of this theory.