A tumor marker is a biomarker that can be used to indicate the presence of cancer or the behavior of cancers.
The ideal tumor marker has the following characteristics:
Specificity to a certain type of tumor
Should detect the malignancy earlier than a clinical diagnosis
Be highly sensitive to avoid false positives
The level of tumor marker should indicate the state of the malignancy to be able to monitor treatment response.
An ideal tumor marker does not exist.
Tumor markers are mainly used in clinical medicine to support a diagnosis and monitor the state of malignancy or reocurrence of cancer.
Tumor markers can be found in bodily fluids or tissue.
Markers can help with assessing prognosis, surveilling patients after surgical removal of tumors, and even predicting drug-response and monitor therapy.
Tumor markers can be molecules that are produced in higher amounts by cancer cells than normal cells, but can also be produced by other cells from a reaction with the cancer.
The markers can’t be used to give patients a diagnosis but can be compared with the result of other tests like biopsy or imaging.
Tumor markers can be proteins, carbohydrates, receptors and gene products.
Proteins include hormones and enzymes.
To detect enzyme tumor markers enzyme activity is measured.
Oncofetal antigens and monoclonal antibodies advantages include organ specificity.
Carbohydrates consists of antigens on and/or secreted from tumor cells, these are either high-molecular weight mucins or blood group antigens.
Receptors are used to determine prognosis and measure how the patient responds to treatment.
Genes or gene products can be analyzed to identify mutations in the genome or altered gene expression.
Uses Tumor markers may be used for monitoring the malignancy.
The level of marker found in the body can be monitored to determine the state of the tumor and how it responds to treatment.
Rising levels of tumor marker does not necessarily reflect a growing malignancy but can result from things like unrelated illnesses.
Tumors can reflect the stage of cancer.
No screening test is wholly specific, and a high level of tumor marker can still be found in benign tumors.
The only tumor marker currently used in screening is PSA.
Diagnostics Tumor markers alone can’t be used for diagnostic purposes, due to lack of sensitivity and specificity.
Tumor markers can detect reoccurring cancers in patients post-treatment.
Tumor markers can be determined in serum or rarely in urine or other body fluids, often by immunoassay. . Assaying tumor markers were significantly improved after the creation of ELISA and RIA techniques and the advancement of monoclonal antibodies.
List of commonly used markers Tumor marker Associated tumor types
Alpha fetoprotein (AFP) germ cell tumor, hepatocellular carcinoma
CA15-3 breast cancer
CA27.29 breast cancer
CA19-9 Mainly pancreatic cancer, but also colorectal cancer and other types of gastrointestinal cancer.
CA-125 Mainly ovarian cancer, but may also be elevated in endometrial cancer, fallopian tube cancer, lung cancer, breast cancer and gastrointestinal cancer.
Calcitonin medullary thyroid carcinoma
Calretinin mesothelioma, sex cord-gonadal stromal tumor, adrenocortical carcinoma, synovial sarcoma
Carcinoembryonic antigen (CEA)-gastrointestinal cancer, cervix cancer, lung cancer, ovarian cancer, breast cancer, urinary tract cancer
CD34 hemangiopericytoma/solitary fibrous tumor, pleomorphic lipoma, gastrointestinal stromal tumor, dermatofibrosarcoma protuberans
CD99 Ewing sarcoma, primitive neuroectodermal tumor, hemangiopericytoma/solitary fibrous tumor, synovial sarcoma, lymphoma, leukemia, sex cord-gonadal stromal tumor
CD117 gastrointestinal stromal tumor, mastocytosis, seminoma
Chromogranin neuroendocrine tumor
Chromosomes 3, 7, 17, and 9p21 bladder cancer
Cytokeratin Many types of carcinoma, some types of sarcoma
Desmin smooth muscle sarcoma, skeletal muscle sarcoma, endometrial stromal sarcoma
Epithelial membrane antigen (EMA)-many types of carcinoma, meningioma, some types of sarcoma
Factor VIII; CD31, FL1, CD34 vascular sarcoma
Glial fibrillary acidic protein (GFAP)glioma (astrocytoma, ependymoma)
Gross cystic disease fluid protein (GCDFP-15-breast cancer, ovarian cancer, salivary gland cancer
HMB-45 melanoma, angiomyolipoma), clear cell carcinoma, adrenocortical carcinoma.
Human chorionic gonadotropin (hCG)-gestational trophoblastic disease, germ cell tumor, choriocarcinoma
immunoglobulin s-lymphoma, leukemia
inhibin sex cord-gonadal stromal tumor, adrenocortical carcinoma, hemangioblastoma
keratin-carcinomas, some types of sarcoma
lymphocyte marker-lymphoma, leukemia
MART-1 (Melan-A) melanoma, steroid-producing tumors (adrenocortical carcinoma, gonadal tumor)
Myo D1 rhabdomyosarcoma, small-blue-round-cell tumor
muscle-specific actin (MSA) myosarcoma (leiomyosarcoma, rhabdomyosarcoma)
neurofilament neuroendocrine tumor; small-cell carcinoma of the lung
neuron-specific enolase (NSE) neuroendocrine tumor; small-cell carcinoma of the lung, breast cancer
placental alkaline phosphatase (PLAP)-seminoma, dysgerminoma, embryonal carcinoma
prostate-specific antigen (PSA)-prostate cancer
S100 protein melanoma, sarcoma (neurosarcoma, lipoma, chondrosarcoma), astrocytoma, gastrointestinal stromal tumor, salivary gland cancer, some types of adenocarcinoma, histiocytic tumor (dendritic cell, macrophage)
smooth muscle actin (SMA) gastrointestinal stromal tumor, leiomyosarcoma
synaptophysin neuroendocrine tumor
thymidine kinase lymphoma, leukemia, lung cancer, prostate cancer
thyroglobulin (Tg) post-operative marker of thyroid cancer
thyroid transcription factor-1 (TTF-1)-all types of thyroid cancer, lung cancer
Tumor M2-PK colorectal cancer, Breast cancer, renal cell carcinoma, lung cancer, pancreatic cancer, esophageal cancer, stomach cancer, cervical cancer, ovarian cancer
vimentin -sarcoma, renal cell carcinoma, endometrial cancer, lung carcinoma, lymphoma, leukemia, melanoma
Account for heterogeneity and activity of a tumor mass.
Changes in levels should reflect changes in tumor mass.
Can be a sensitive and cost effective method for predicting prognosis in patients with cancer.
Serial assessments assist in predicting response to therapy and to failure of treatment as well.