Serum Tumor Markers

Tumor markers are molecules that may be present in higher than usual concentrations in the tissue, serum, urine, or other body fluids of patients with cancer. Such substances are measured qualitatively or quantitatively by chemical, immunological, or molecular biological methods.
Clinically, an ideal tumor marker should be both specific for a given type of cancer and sensitive enough to detect small tumors for early diagnosis or during screening. 

Include alkaline phosphatase (ALP), lactate dehydrogenase (LDH), neuron specific enolase (NSE), prostatic acid phosphatase (PAP) and prostate specific antigen (PSA). ALP is used in diagnosis and treatment of the liver, bone, intestinal and parathyroid diseases. LDH is a marker for hemolysis. Increased in approximately 50% of patients with various solid carcinomas, especially in advanced stages, high grade lymphomas and acute leukemias. NSE is used as an auxiliary test in the diagnosis of small cell carcinoma, carcinoids, islet cell tumors and neuroblastomas.

Proteins that are produced during fetal life. In certain cancers, these proteins reappear, revealing that certain genes are reactivated as the result of the malignant transformation of cells. Examples include AFP and CEA.

The cytokeratins are a group of approximately 20 proteins that make up the cytoskeletal intermediate filaments of epithelial cells and cells of epithelial origin.

CA 19-9 is an example which is a marker for gastrointestinal cancers and is used primarily in patients with pancreatic carcinoma.

Carbohydrate-related tumor markers may be antigens on the tumor cell surface, or secreted by the tumor cells. It is used as an aid in monitoring patients previously treated for stage II or III breast cancer.
The production of hormones in cancer involves two separate routes. First, the endocrine tissue that normally produces it produces excess amounts of a hormone. Second, a hormone may be produced at a distant site by a non-endocrine tissue that normally does not produce the hormone. 

Included in this group of tumor markers are proteins that are not enzymes or hormones and are not high in carbohydrate content. Clinically useful members are monoclonal immunoglobulin (paraprotein), β2-microglobulin, C-peptide, chromogranins, thyroglobulin, human epididymis 4. 

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