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Cancer is a generic term for a large group of diseases that can affect any part of the body. Other terms used are malignant tumours and neoplasms. Cancer arises from cells. Cells are body’s basic building blocks. They continuously divide from one to two to four….so on. This cell division is essential for body growth as well as for the replacement of dead and damaged cells. Normally our body has control over the cell division. Hence, there is a balance between newly forming cells and number of dead/damaged cells. But, in presence of any carcinogenic (cancer-causing) stimulus, cells divide in an uncontrolled manner and this balance is disrupted. This loss of normal growth control gives rise to cancer. The transformation from a normal cell into a tumour cell is a multistage process, typically a progression from a pre-cancerous lesion to malignant i.e. cancerous tumours. Another differentiating feature of cancerous cells is their ability to spread through body.
Cancer can cause a variety of symptoms. Possible signs of cancer include the following:
At any given point, there are around 25 lac cases of cancer in India. Every year around 7-9 lac new cases of cancer are diagnosed in India. These figures may be an underestimation of the true prevalence of cancer, owing to lack of statistical data.
Cancer cells can spread to almost any part of the body. Cancer cells frequently spread to lymph nodes (rounded masses of lymphatic tissue) near the primary tumor (regional lymph nodes). This is called lymph node involvement or regional disease. Cancer that spreads to other organs or to lymph nodes far from the primary tumor is called distant metastatic disease. The most common sites of metastasis from solid tumors are the lungs, bones, liver, and brain. Some cancers tend to spread to certain parts of the body. For example, lung cancer often metastasizes to the brain or bones, and colon cancer frequently spreads to the liver. Prostate cancer tends to spread to the bones. Breast cancer commonly spreads to the bones, lungs, liver, or brain. However, each of these cancers can spread to other parts of the body as well. Because blood cells travel throughout the body, leukemia, multiple myeloma, and lymphoma cells are usually not localized when the cancer is diagnosed. Tumor cells may be found in the blood, several lymph nodes, or other parts of the body such as the liver or bones. This type of spread is not referred to as metastasis.
No. A metastatic tumor always starts from cancer cells in another part of the body. In most cases, when a metastatic tumor is found first, the primary tumor can be found. The search for the primary tumor may involve lab tests, x-rays, and other procedures. However, in a small number of cases, a metastatic tumor is diagnosed but the primary tumor cannot be found, in spite of extensive tests. The pathologist knows the tumor is metastatic because the cells are not like those in the organ or tissue in which the tumor is found. Doctors refer to the primary tumor as unknown or occult (hidden), and the patient is said to have cancer of unknown primary origin (CUP). Because diagnostic techniques are constantly improving, the number of cases of CUP is going down.
To determine whether a tumour is primary or metastatic, a pathologist examines a sample of the tumour under a microscope. In general, cancer cells look like abnormal versions of cells in the tissue where the cancer began. Using specialized diagnostic tests, a pathologist is often able to tell where the cancer cells came from. Markers or antigens found in or on the cancer cells can indicate the primary site of the cancer. Metastatic cancers may be found before or at the same time as the primary tumour, or months or years later. When a new tumour is found in a patient who has been treated for cancer in the past, it is more often a metastasis than another primary tumour.
Cancers are capable of spreading throughout the body by two mechanisms: Invasion and Metastasis. Invasion refers to the direct migration and penetration by cancer cells into neighboring tissues. Metastasis refers to the ability of cancer cells to penetrate into lymphatic and blood vessels, circulate through the bloodstream, and then invade normal tissues elsewhere in the body.
When cancer cells spread and form a new tumour in a different organ, the new tumour is a metastatic tumour. The cells in the metastatic tumour come from the original tumour. For example, if breast cancer spreads to the lungs, the metastatic tumour in the lung is made up of cancerous breast cells (not lung cells). In this case, the disease in the lungs is metastatic breast cancer (not lung cancer). Under a microscope, metastatic breast cancer cells generally look the same as the cancer cells in the breast.
The site or the organ in the body where cancer begins is called as the primary site of cancer. The original tumour or cancerous growth is called the primary cancer or primary tumor. It is usually named for the part of the body or the type of cell in which it begins.
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