What is Cancer?
Cancer can be considered as a disease acquired from genetic damage that disturbs the mechanisms that maintain normal cellular behavior, disrupt the normal control of cell division and death, and result in abnormal growth. Cancer or malignancy differs from a benign tumor in the rate and pattern of growth as well as the characteristic of the malignant cells. This is discussed further under the characteristics of Benign and Malignant Tumors.
Development of Cancer
The genetic damage in cancerous cells may be in the form of mutations that can activate cancer-causing genes, deactivate cancer-preventing genes, or translocations resulting in altered functions of genes. Certain mutations can lead to dysfunction of genes that normally prevent mutations in other genes, or repair the damaged DNA, leading to uncontrolled mutations in the cells and resulting in cancer.
Cancer Risk Factors
The genetic damage leading to cancer can result from chronic exposure to certain carcinogens through :
- lifestyle factors like smoking
- food and beverages like alcohol, possibly large amounts of smoked foods (1)
- drugs like cytotoxic drugs, estrogen pills
- infections like the hepatitis C virus, HIV
- ionizing radiation
- environmental and occupational exposure to carcinogens like asbestos, arsenic
A family history of cancer is one of the major risk factors as well. The presence of other risk factors may therefore increase the likelihood of developing of cancer.
Growth and Spread of Cancer
The mutated cancer cells multiply quickly and form a tumor, which is called the primary tumor. Once a primary tumor has developed, it starts to stimulate growth of blood vessels to support the growing cells with nourishment and oxygen and grows further.
As the tumor grows it invades the adjacent tissues. The tumor cells also enter into the lymphatic vessels and are carried to the lymph nodes that drain the region. Here they get trapped and start multiplying to form another tumor. Some cancer cells may also invade blood vessels and enter the bloodstream. These cells are transported to various parts of the body (distant metastasis), where they get lodged and then multiply to form secondary tumors.
In patients with suspected cancer, a lesion may be found on physical examination or on radiographic studies. A biopsy then obtained from the lesion and histopathological examination is done to confirm the malignant nature of the lesion. Once the diagnosis is confirmed clinically or pathologically, the oncologist proceeds with pretreatment evaluations, which is the staging and grading of the cancer.
- Risk Factors in Gastric Cancer. Pubmed