Cytokeratin 7 (CK7) is a protein that is made mostly by cells in the lung, breast, female reproductive organs (ovaries and endometrium), thyroid gland, and salivary glands (for example the parotid gland). It is also produced by some cells in the stomach and pancreas.
Cytokeratin 7 is a type of protein called a keratin. These proteins are made mostly by cells on the surface of a tissue called epithelial cells. Another name for this protein is CK7.
Most tumours from the lung, breast, female reproductive organs, thyroid gland, and salivary glands will produce cytokeratin 7. Some tumours from the stomach and pancreas will also produce this protein.
Pathologists perform a test called immunohistochemistry to look for cells producing cytokeratin 7. If the cells in your sample produce this protein, your report will describe the cells as positive or reactive. If they do not produce this protein, your report will describe the cells as negative or non-reactive.
This test is important if the tumour cells have traveled to a lymph node or distant body site or if the tumour cells look very abnormal. The movement of tumour cells to another part of the body is called metastasis. This test helps a pathologist decide where the tumour started.