Interphase Analysis of Chromosome 11 in Human Pituitary Somatotroph Adenomas by Direct Fluorescence In Situ Hybridization

Chromosome 11 numerical abnormalities were detected by fluorescencein situ hybridization (FISH) technique in four surgically removed pituitary somatotroph adenomas from patients clinically associated with acromegaly. The tumors were diagnosed by histology, immunocytochemistry, and electron microscopy, and included two densely granulated somatotroph (DG-SM) and two sparsely granulated somatotroph (SG-SM) adenomas. For demonstration of chromosome 11, the direct FISH technique was applied on imprints from fresh adenoma tissue fixed in acetone using an α-satellite specific centromeric probe. The slides were studied with a fluorescence microscope and the percentages of positive nuclei with aberrant fluorescent signals were counted. All tumors exhibited numerical chromosomal abnormalities in 8–23% of their cell population and included nuclei containing 1–3 extra chromosome 11 copies. The SG-SM adenomas exhibited more prominent abnormalities compared with the DG-SM adenomas. We conclude that numerical chromosome 11 abnormalities represent a frequent event among somatotroph adenomas with a tendency for higher frequency in SG-SM adenomas.