IHC

What is PAX5?

PAX5 is a protein that acts as a transcription factor, which means it helps control when certain genes are turned on or off in a cell. It plays an important role in the early development of the immune system by guiding immature blood cells to become B cells, a type of white blood cell that …
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AE1/AE3: Definition

AE1/AE3 is a laboratory test used by pathologists to help identify the origin of a tumour. It works by detecting proteins called cytokeratins — structural proteins found inside epithelial cells, which line the surfaces of organs and glands throughout the body. AE1/AE3 is not a single protein — it is a combination of two antibodies, …
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What is CDX-2?

CDX2 is a protein made by cells that line the inside of the gastrointestinal tract, including the small intestine and the colon. It plays an important role in controlling how these intestinal cells grow and develop. Why do pathologists test for CDX2? Pathologists test for CDX2 to help determine if cells seen in a tissue …
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Synaptophysin: Definition

Synaptophysin is a protein found in certain types of cells, particularly those in the nervous system and in neuroendocrine cells, which are specialized cells that release hormones in response to nerve signals. Synaptophysin is located on small storage sacs called synaptic vesicles, which are used to send messages between nerve cells or to release hormones. Because …
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What is PAX8?

PAX8 is a protein that helps control the activity of genes in certain types of cells. It acts as a transcription factor, meaning it turns genes on or off to guide how cells grow, develop, and function. PAX8 is especially important during early development and is involved in forming organs such as the thyroid gland, …
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TTF-1: Definition

TTF-1 stands for thyroid transcription factor-1. It is a protein that helps the lungs and thyroid gland develop and work normally. Pathologists test for TTF-1 to learn whether a tumor started in the lung or the thyroid. This article explains what TTF-1 is, which cells and tumors make it, how pathologists test for it, and …
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GATA-3: Definition

GATA3 (GATA binding protein 3) is a protein found in the nucleus of specific cells. It plays a crucial role in regulating how these cells grow and develop by controlling the activity of specific genes. GATA3 is especially important in the normal development of breast tissue, the urinary tract (urothelium), and certain immune cells.​ What …
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S100: Definition

S100 is the name of a family of proteins found inside certain types of cells in the body. These proteins help cells respond to changes in their environment by regulating processes like growth, movement, and communication. The name “S100” comes from the fact that the proteins are soluble in a solution made with 100% saturated …
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What is p40?

p40 is a specialized protein that helps pathologists identify specific types of cells, especially squamous cells, which are found on surfaces like the skin, the lining of the mouth and throat, and parts of the lungs and urinary tract. p40 is a shortened version (or “isoform”) of another protein called p63, but it is more …
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Immunoreactivity: Definition

Immunoreactivity is a term pathologists use to describe how cells or tissues respond to a special laboratory test called immunohistochemistry (IHC). In this test, antibodies are applied to a tissue sample to look for specific proteins. If the protein being tested is present, the antibody will attach to it, and the cells will change color …
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