Chromogranin A and B in adenomas of the pituitary: An immunohistochemical study of 42 cases

Forty-two pituitary adenomas (10 prolactinomas; three ACTH-, nine GH-, two FSH- and two TSH-secreting adenomas; and 16 clinically nonfunctioning null cell adenomas) were investigated immunohistochemically with antibodies against chromogranin A and B as well as ACTH, GH, prolactin (PRL), FSH, LH, TSH, and α-HCG antibodies. For the demonstration of chromogranin B, two different antibodies were used-e.g., a polyclonal antihuman antibody and an antiserum against a synthetic peptide (DK-21, chromogranin B 306-326) present in the chromogranin B amino acid sequence. All tumors were positive for both chromogranin B antibodies. Chromogranin A was found in FSH- (two of two) and TSH- (two of two) secreting adenomas; it was also found in a focal distribution in ACTH- (one of three) and GH- (four of nine) secreting adenomas. Thirteen of 16 null cell adenomas contained chromogranin A, whereas no chromogranin A was found in prolactinomas. We conclude that null cell adenomas may arise either from FSH/LH or TSH cells (null cell adenomas with both chromogranin A and B positivity) or from ACTH, GH, or PRL cells (the respective tumors are only positive for chromogranin B). Chromogranin B may be used as a universal marker for pituitary adenomas.