Chromogranin A and B and secretogranin II in medullary carcinomas of the thyroid

We have studied the presence of chromogranins A and B and secretogranin II in medullary carcinomas of the thyroid using the methods of immunoblotting and immunohistochemistry. All three antigens were identified by immunoblotting. Chromogranin A and secretogranin II behaved identically to the adrenal antigens in electrophoresis, whereas the molecular size of chromogranin B in the thyroid tissue appeared slightly smaller, possibly due to a higher degree of proteolytic processing. In immunohistochemistry, positive staining was obtained with all three antigens throughout the tumor tissue. All three antigens, as well as the hormone calcitonin, were apparently present in the same cells. Our study suggests that in addition to chromogranin A, the other two antigens (chromogranin B and secretogranin II) may also be useful markers for tumors arising from endocrine tissues.