Introduction
Tumor markers are substances that are measurable in the blood and can indicate the presence of tumors. They are mainly produced by malignant cells in the body and can thus be a point of reference for a diagnosis. Tumor markers can either be synthesized by the tumor itself, or they can arise as a reaction of the tissue.
Since they do not always correlate reliably with the presence of a tumor, tumor markers are usually not used for diagnosis. In addition, most tumor markers also increase in certain benign diseases and are therefore not useful for early diagnosis of a tumor disease. However, there are some markers that are used to monitor the course of tumor treatment and allow reliable statements on the prognosis and effectiveness of the therapy. There are many different tumor markers that are specific for certain organs.
CEA
The Carcinoembryonic Antigen (CEA) as tumor marker was first isolated from cells of a colorectal carcinoma in 1965. It is a family of glycoproteins that are incorporated into their own cell membrane by the cells that produce CEA and release it into the blood. For this reason CEA is detectable in the corresponding cells as well as in the blood.
Since it is a very unspecific tumor marker, it cannot be used for the early diagnosis of a tumor. However, it has proven to be effective in post-operative care and therapy monitoring. CEA is particularly specific for colorectal cancer and thyroid carcinoma.
However, there are also benign diseases such as inflammation of the liver, stomach, pancreas and lungs, as well as alcohol-induced liver cirrhosis, which can lead to an increase in CEA. Smokers can also have an increase in CEA in their blood. Permanently elevated CEA values, however, indicate a malignant tumor.
HCG
Human chorionic gonadotropin (HCG) as a tumor marker is produced by fetal cells at the beginning of pregnancy. It is used to stimulate the ovaries, thereby stimulating their hormone production and thus maintaining the pregnancy. In the absence of pregnancy, elevated HCG levels indicate a malignant tumor of the ovaries, but also benign ulcers of the ovaries, or in men, a testicular tumor.
This is usually a chorionic carcinoma. Elevated HCG levels are also detectable in liver tumors (hepatoblastoma) in children. The bladder mole in women is an example of benign diseases associated with elevated HCG levels.