p63 is a protein made by both normal cells and tumour cells. After it is made, p63 is held in a part of the cell called the nucleus. Pathologists use a test called immunohistochemistry to see p63 inside cells. The results of this test are used with other information to make a diagnosis. Normal tissues that make p63 include skin, salivary gland, breast, prostate, and bladder. Tumours from the skin, salivary gland, and bladder also make p63. Your pathologist may perform immunohistochemistry for p63 to confirm that the tumour comes from one of these organs.