November 14, 2023

p40 is a protein that is made by many different kinds of normal healthy cells including squamous cells, basal cells, and myoepithelial cells. Tumours that start from these types of specialized cells also make p40. Once the p40 protein is made it is held in a part of the cell called the nucleus. The nucleus is an important part of the cell because it holds most of the cells’ genetic material (DNA).

Immunohistochemistry (IHC) is a test pathologists perform to see p40-producing cells in a tissue sample. When combined with other immunohistochemical markers, this test allows pathologists to determine if the cells they are seeing under the microscope are related to any of the cell types that normally produce this protein. This test is particularly helpful when examining a tumour under the microscope because tumours made up of squamous cells, basal cells, or myoepithelial cells are more likely to produce p40 while tumours from other locations are not. Pathologists use the results of this test combined with other features to make a diagnosis.

About this article

This article was written by doctors to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report. For a complete introduction to your pathology report, read this article.

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