Wednesday, January 4, 2012

Chromogranin A :The Test

Chromogranin A test is a tumor marker.  The oncologist may order this test along with other tests if they suspect a carcinoid tumor,pheochromocytoma, and neurendocrine tumor.

Carcinoid tumor are derived from primitive stem cells in the gut wall but can be seen in other organs,[1] including the lungs,[2] mediastinum, thymus,[3] liver, pancreas, bronchus, ovaries,[4] prostate,[5] and kidneys.[6] In children, most tumors occur in the appendix and are benign and asymptomatic.
Most carcinoid tumors are slow growing and indolent without symptoms. Nevertheless, aggressive and metastatic disease (eg, to the brain) does occur. Even tumors in the appendix can metastasize.[7, 8] Depending on the size and location, carcinoid tumors can cause various symptoms, including carcinoid syndrome. Carcinoid tumors of the ileum and jejunum, especially those larger than 1 cm, are most prone to produce this syndrome, at least in adults.

Pheochromocytoma is a neuroendocrine tumor of the medulla of the adrenal glands (originating in the chromaffin cells), or extra-adrenal chromaffin tissue that failed to involute after birth [1] and secretes excessive amounts of catecholamines, usually noradrenaline (norepinephrine), and adrenaline (epinephrine) to a lesser extent.[2] Extra-adrenal paragangliomas (often described as extra-adrenal pheochromocytomas) are closely related, though less common, tumors that originate in the ganglia of the sympathetic nervous system and are named based upon the primary anatomical site of origin.

Neuroendocrine tumors (NETs) are neoplasms that arise from cells of the endocrine (hormonal) and nervous systems. Many are benign, while some are cancers. They most commonly occur in the intestine, but are also found in the lung and the rest of the body.
Although there are many kinds of NETs, they are treated as a group of tissue because the cells of these neoplasms share common features, such as looking similar, having special secretory granules, and often producing biogenic amines and polypeptide hormones.[1]

The Chromogranin A  may be ordered in combination with or in place of 5-HIAA to help diagnose carcinoid tumors. It is also used to help monitor the effectiveness of treatment and detect recurrence of this tumor. Sometimes it may be ordered with specific hormones, such as catecholamines, to help diagnose and monitor a pheochromocytoma. It may also be used to detect the presence of other neuroendocrine tumors, even those that do not secrete hormones.

Chromogranin A concentrations are normally low.  An increased level in a symptomatic person may indicate the presence of a tumor but will not tell the doctor what type it is or where it is. The quantity of CgA is not associated with the severity of a person's symptoms but is associated with the tumor burden - the mass of the tumor.
If concentrations of CgA are elevated prior to treatment and then fall, then treatment is likely to have been effective. If monitored levels begin to rise, then the person may have a recurrence of the tumor.

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