GAWK

Chromogranin A (CgA)

• a secretory granule which is located alongside specific hormones in large dense-core vesicles of neuronal and neuroendocrine cells

Chromogranin B (CgB)

• like CgA, widely distributed in neuroendocrine cells, although CgA seems to be more widespread

Plasma CgA may be elevated in neuroendocrine tumours

• one study revealed that plasma CgA was elevated in 94% of endocrine pancreatic tumours
• there is study evidence that elevated CgA levels are even more frequent (99%) in malignant carcinoid and gastroenteropancreatic tumours (99%) - the highest levels seen in metastatic carcinoid particularly midgut)

Plasma CgB (and its 74-amino-acid fragment termed GAWK) is generally a better marker for benign insulin-producing tumours than CgA.

Staining for the chromogranins in different neuroendocrine tumours has revealed that CgA seems more ubiquitous than CgB with the exception of the CgB-staining pituitary lactotrophs and some pancreatic beta-cell tumours.

Reference:

1. Endocr Relat Cancer. 2004 Mar;11(1):1-18.