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Cancer is a disease characterized by uncontrolled, uncoordinated and undesirable cell division. Unlike normal cells, cancer cells continue to grow and divide for their whole lives, replicating into more and more harmful cells.
The abnormal growth and division observed in cancer cells is caused by damage in these cells' DNA. As cancer cells divide and replicate themselves, they often form into a clump of cancer cells known as a tumor. Tumors cause many of the symptoms of cancer by pressuring, crushing and destroying surrounding non-cancerous cells and tissues.
Tumors are of two forms:
Benign tumors are not cancerous, thus they do not grow and spread to the extent of cancerous tumors. Benign tumors are usually not life threatening. Malignant tumors, on the other hand, grow and spread to other areas of the body. The process whereby cancer cells travel from the initial tumor site to other parts of the body is known as metastasis.
Stages of Cancer:-
There are five progressively severe stages: 0, I, II, III, and IV.
Stage 0 cancer:- The cancer that is just beginning, involving just a few cells.
Stages I, II, III, and IV:-It represent progressively more advanced cancers, characterized by larger tumor sizes, more tumors, the aggressiveness with which the cancer grows and spreads, and the extent to which the cancer has spread to infect adjacent tissues and body organs.
Another popular staging system is known as the TNM system, a three dimensional rating of cancer extensiveness. Using the TNM system, doctors rate the cancers they find on each of three scales, where T stands for tumor size, N stands for lymph node involvement, and M stands for metastasisÂ
There are two common approaches used to treat almost all types of cancer. These two treatments are chemotherapy and radiation therapy.
Â Chemotherapy is one of the most commonly used methods to treat cancer patients. It is commonly prescribed for patients whose cancer is not localized. It can be used to reduce the symptoms and pain associated with cancer as well as to slow the growth of cancerous tumors. In some circumstances chemotherapy may even kill spreading cancerous cells.
Radiation therapy is a method of treating cancer that utilizes radiation energy. It is most commonly used to treat localized cancers. The goal of radiation therapy is to kill cancer cells or at least limit their ability to grow and divide by damaging their genetic material. Some normal, healthy cells can also become damaged radiations. Also, healthy cells that do sustain damage during radiation treatment are usually able to repair their genetic material when treatment ends.
Â Patient who have a specific form of cancer will undergo a series of tests and procedures to rule-out a cancer. The sample of tissue or fluid from the area believed to contain a cancerous tumor so that it may be analyzed in the laboratory under a microscope. This collection and observation procedure is known as a biopsy.
Types of cancer:-
Most common types of cancerÂ are:-
Colon and Rectal cancer
Kidney (Renal Cell) Cancer
Links between mutations and cancer
a. Cells do not require mutations to become cancerous but acquire them as they divide.Â
b. Only a mutation can stop a cell once it becomes cancerous.Â
c. Some mutations cause cells to lose control over cell division.Â
d. Any point mutation will cause a cell to start proliferating without control.Â
e. Cells lose the ability to mutate their DNA and evolve once they become cancerous.
Cancer is a disease of genes gone awry. Genes that control the orderly replication of cells become damaged, allowing the cell to reproduce without restraint and eventually to spread into neighboring tissues and set up growths throughout the body.Â
All cancer is genetic, in that it is triggered by altered genes. However, just a small portion of cancer is inherited: a mutation carried in reproductive cells, passed on from one generation to the next, and present in cells throughout the body. Most cancers come from random mutations that develop in body cells during one's lifetime - either as a mistake when cells are going through cell division or in response to injuries from environmental agents such as radiation or chemicals
Differences between hereditary and sporadic forms of cancer Â
Hereditary cancerÂ often occur earlierÂ than the sporadic form of the same cancer, so experts often recommend different screening,Â at a youngerÂ age for peopleÂ with hereditary cancer in their family.
Hereditary cancers are caused in part by gene changes passed on from parents to theirÂ children. Other blood relatives may share these sameÂ gene changes.Â Sporadic cancers are believed to arise from geneÂ damage acquired fromÂ environmental exposures, dietary factors, hormones, normal aging, and other influences. Most acquiredÂ gene changes are not shared among relatives or passed on to children.
Individuals who have inherited a gene change may be at a higher risk for more than one type of cancer. For cancer survivors,Â this may affect cancer treatment options or follow-up care.
Forms of hereditary colon cancer Â ( FAP - familial polyposis Â and HNPCC - Hereditary Nonpolyposis Colon Cancer) and genes mutated in them Â Â
There are two major types of hereditary disorders that lead to colorectal cancers, familial adenomatous polyposis (also known as FAP) and hereditary non-polyposis colorectal cancer (HNPCC).
Genes mutated in HNPCC: -
Many patients have similar family histories, specific criteria must be met and certain genetic abnormalities must be present for a family to be classified as HNPCC. The genes that have been identified as responsible for HNPCC are MSH1, MSH2, PMS1, and PMS2. Individuals with a mutation in any one of these genes have an estimated lifetime risk of developing colon cancer. People with HNPCC are most likely to develop cancer on the right side of the colon, unlike most sporadic cases, which develop on the left side of the colon.
Gene mutated in FAP:-
The gene for FAP is on the long arm of chromosome 5 and is called theÂ APCÂ gene.
APC is aÂ tumour suppressor gene, acting as a "gatekeeper" to prevent development of tumours. Mutation ofÂ APCÂ also occurs commonly in incident cases of colorectal carcinoma.Although the polyps are inherently benign, the first step that takes place is the inherited APC mutation. Often, the remaining "normal"Â alleleÂ is mutated or deleted, accelerating generation of polyps. Further mutations (e.g. inÂ p53 orÂ kRAS) to APC-mutated cells are much more likely to lead to cancer than they would in non-mutatedÂ epithelialÂ cells.