In the clinical world, the term cancer refers to more than 100 different diseases. Each malignant tissue is unique, due to heterogeneity resulting from genetic basis, microenvironment and selection pressure within the tissue. Cancer develops in a multistep process and can be understood from an evolutionary perspective, as mutations, selection and genetic drift are the drivers of its development. Tumor initiation is the result of changes in a normal, healthy cell that acquires the ability to grow uncontrollably. This is followed by neoplastic proliferation and the development of tumor tissue. Cancer stem cells play a key role in this process, because they have the ability to self-renew and form heterogeneous cells in the tumor. The clonal expansion of a clone leads to genetic and epigenetic changes that shape the course of the disease. By introducing a strong source of artificial selection in the form of drugs or radiation, oncologists change the dynamics of cancer cells. Treatment usually results in massive cell death, which represents a selective pressure for proliferating cells capable of surviving such treatment. In the treatment of cancer, the development of resistant mutants occurs. With the help of development and research in the field of clonal evolution of cancer, we can use various biomarkers to help diagnose the progression of the disease. Frequent tissue sampling and correct characterization of the degree of tissue heterogeneity are also important. Newer treatment methods include targeted therapy, combined therapy, genomic analysis, and various methods of drug delivery. In the future, a personalized approach to cancer treatment is likely to become more prevalent.
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