A 19-year-old man with blurred vision,
headache, and no signs or symptoms of
hormone excess was found to have a
pituitary adenoma. The
tumor was removed by a transfrontal approach. He had postoperative
radiation therapy, but subsequently had three recurrences, all removed surgically. By histology, the
tumor was a chromophobic, slightly acidophilic
pituitary adenoma. Immunohistochemistry revealed the presence of
adrenocorticotropin (
ACTH) in all four biopsies, alpha-subunit of
glycoprotein hormones, and, to a lesser extent,
follicle-stimulating hormone (FSH) and
luteinizing hormone (LH) in the third and fourth
tumor resection specimens. Ultrastructurally, the
tumor had typical features of a silent
corticotroph adenoma subtype 2. In tissue culture, the second, third, and fourth specimens released
ACTH, alpha-subunit, FSH, and LH and responded to
corticotropin-releasing hormone with increased release of
ACTH, alpha-subunit, FSH, and LH. To our knowledge only one silent
corticotroph adenoma has been reported previously which expressed plurihormonality. Change in immunohistochemical profile in malignant
tumors is a well-known phenomenon; however, it was not reported previously in benign
pituitary adenomas. The factors accounting for changing
tumor phenotype are unknown.