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3D medical illustration depicting the TNM stages in breast cancer. Cancer staging can be divided into a clinical stage and a pathologic stage. In the TNM (Tumor, Node, Metastasis) system, clinical stage and pathologic stage are denoted by a small "c" or "p" before the stage (e.g., cT3N1M0 or pT2N0).
Tumor progression is the third and last phase in tumor development. [1] This phase is characterised by increased growth speed and invasiveness of the tumor cells. As a result of the progression, phenotypical changes occur and the tumor becomes more aggressive and acquires greater malignant potential.
The central role of DNA damage and epigenetic defects in DNA repair genes in carcinogenesis. DNA damage is considered to be the primary cause of cancer. [17] More than 60,000 new naturally-occurring instances of DNA damage arise, on average, per human cell, per day, due to endogenous cellular processes (see article DNA damage (naturally occurring)).
Silencing of a DNA repair gene by hypermethylation or other epigenetic alteration appears to be a frequent step in progression to cancer. As summarized in a review, [ citation needed ] promoter hypermethylation of DNA repair gene MGMT occurs in 93% of bladder cancers, 88% of stomach cancers, 74% of thyroid cancers, 40%-90% of colorectal cancers ...
This is a step toward tumor progression. [2] [3] In order for a tumor cell to survive, it must decrease its expression of tumor suppressor genes such as p53, BRCA1, BRCA2, RB1, or the fas receptor. [4] [5] A tumor suppressor would trigger an apoptotic pathway in a cancer cell if there were DNA damage, polyploidy, or uncontrolled cell growth.
The TNM Classification of Malignant Tumors (TNM) is a globally recognised standard for classifying the anatomical extent of the spread of malignant tumours (cancer). It has gained wide international acceptance for many solid tumor cancers, but is not applicable to leukaemia or tumors of the central nervous system .