Cancer (malignant tumor) is a neoplasm caused by abnormal cell growth (usually arises from one abnormal cell). Cells lose their normal control mechanisms and acquire the ability to continuously multiply, invade nearby tissues, migrate to distant parts of the body and promote the formation of new blood vessels that provide cells with nutrients. Tumor (malignant) cells can develop from any tissue in the body.

In the process of their growth and reproduction, malignant cells form a tumor - an accumulation of tumor tissue, which captures and affects healthy surrounding tissues. The term "tumor" refers to an abnormal growth or proliferation of tissue. Tumors can be malignant or benign. Malignant cells from the original (original) site can spread throughout the body (metastasize).

Malignant tumors can be classified into cancers of the blood and hematopoietic tissues (leukemia and lymphoma) and "solid" tumors (solid mass of cells), often called cancer. Cancer also includes carcinomas and sarcomas.