Pathology dictionary

What is p53?

p53 is a protein made by both normal cells throughout the body. p53 is a type of protein called a tumour suppressor. Cells that cannot make normal p53 may turn into cancer cells overtime.

After it is made, p53 is held in a part of the cell called the nucleus. Pathologists use a test called immunohistochemistry to see p53 inside cells. The results of this test are used with other information to make a diagnosis.

When examined by immunohistochemistry, p53 can show three different patterns of expression:

  1. Wild type – This is the normal pattern for p53. In this pattern of expression, p53 can be seen in some but not all normal cells.
  2. Over expression – This is an abnormal pattern. In this pattern, p53 can be seen in all the abnormal cells.
  3. No expression – This is an abnormal pattern. In this pattern, p53 is not seen in any of the abnormal cells. Some pathologists call this the “null” pattern.

Over expression or no expression of p53 can be seen in both pre-cancerous conditions and cancers. The gene responsible for producing the p53 protein (also called p53) is altered (mutated) is many kinds of human cancers. These mutations cause the p53 to be either over expressed or not expressed in cancer cells.

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