Cancer
KEY POINTS

Biology of Cancer Cancer encompasses a broad range of diseases of multiple causes that can arise in any cell of the body capable of evading regulatory controls of proliferation and differentiation. Two major dysfunctions present in the process of cancer are (1) defective cell proliferation (growth) and (2) defective cell differentiation. Cancer cells usually proliferate at the same rate of the normal cells of the tissue from which they arise. However, cancer cells divide indiscriminately and haphazardly and sometimes produce more than two cells at the time of mitosis. Through differentiation, cells become capable of performing only specific functions. o Proto-oncogenes are normal cell genes that regulate normal cell processes to keep them in their mature, functioning state. o When proto-oncogenes are mutated, they can begin to function as oncogenes (tumor-inducing genes). Tumors can be classified as benign or malignant. o Benign neoplasms are well-differentiated. o Malignant neoplasms range from well-differentiated to undifferentiated.

Development of Cancer The stages of cancer include initiation, promotion, and progression. o The first stage, initiation, is a mutation in the cell’s DNA genetic structure following exposure to a chemical, radiation, or viral agent. The mutation may also be inherited. o Promotion, the second stage in the development of cancer, is characterized by the reversible proliferation of the altered cells. o Progression, the final stage, is characterized by increased growth rate of the tumor, increased invasiveness, and spread of the cancer to a distant site (metastasis). Metastasis is a multistep process in which tumor cells travel to distant sites via lymphatic and hematogenous routes. The most frequent sites of metastasis are lungs, bone, brain, liver, and adrenal glands.

Role of the Immune