ABSTRACT
Chromogranin A (CgA) is the most abundant granin in gastroenteropancreatic neuroendocrine tumors (GEP-NETs). As a tumor marker is moderately sensitive and nonspecific. Despite the limitations of testing methods, which require careful interpretation, especially in the case of gastrinomas, patients treated with somatostatin analogues, and poorly differentiated tumors, it is the best tumor marker in GEP-NETs and may be of value in other tumors with neuroendocrine differentiation. CgA may be used as a marker in blood or tissue samples through immunohistochemical techniques. CgA levels correlate with tumor burden and extension and may be used for diagnosis and monitoring of GEP-NETs, especially midgut carcinoids and endocrine pancreatic tumors. It is also useful as a prognostic marker for detection of recurrence and monitoring of response to different treatments.
Subject(s)
Biomarkers, Tumor/blood , Chromogranin A/blood , Gastrointestinal Neoplasms/chemistry , Neoplasm Proteins/blood , Neuroendocrine Tumors/chemistry , Pancreatic Neoplasms/chemistry , Adrenal Gland Neoplasms/blood , Carcinoma, Medullary/blood , Chromogranin A/physiology , Chromogranins/classification , Chromogranins/metabolism , Enzyme-Linked Immunosorbent Assay , Gastrinoma/blood , Gastrinoma/chemistry , Gastrinoma/therapy , Gastrointestinal Neoplasms/blood , Gastrointestinal Neoplasms/therapy , Humans , Immunoradiometric Assay , Neuroendocrine Tumors/blood , Neuroendocrine Tumors/therapy , Neurons/metabolism , Pancreatic Neoplasms/blood , Pancreatic Neoplasms/therapy , Pheochromocytoma/blood , Prognosis , Radioimmunoassay , Sensitivity and Specificity , Thyroid Neoplasms/blood , Tumor BurdenABSTRACT
Antibodies to six specific regions of the chromogranin A (CgA) molecule were used to study their immunoreactivity in human neuroendocrine (NE) tumors. Tissue specimens from endocrine pancreatic tumors (n = 14), duodenal carcinoids (n = 2), bronchial carcinoids (n = 5), ileal carcinoids (n = 5) appendix carcinoids (n = 2), medullary thyroid carcinomas (n = 6), parathyroid adenomas (n = 2), and pheochromocytomas (n = 8) were analyzed. The results showed that the NE tumor types expressed varying numbers of CgA fragments. A variation in frequency of the expression of immunoreactive cells was sometimes seen also within the same tumor type. The midportion fragment CgA 176-195 (chromacin) was the only fragment expressed in all tumors. Benign and malignant tumors expressed different patterns, being especially true of insulinomas and pheochromocytomas. These findings suggest that region-specific antibodies to CgA fragments can be used as a diagnostic tool for the characterization of NE tumors.