INTERPHASE ANALYSIS OF CHROMOSOME-11 IN HUMAN PITUITARY SOMATOTROPH ADENOMAS BY DIRECT FLUORESCENCE IN-SITU HYBRIDIZATION

Chromosome 11 numerical abnormalities were detected by fluorescence in situ hybridization (FISH) technique in four surgically removed pituit ary somatotroph adenomas from patients clinically associated with acro megaly. The tumors were diagnosed by histology, Immunocytochemistry, a nd electron microscopy, and included two densely granulated somatotrop h (DG-SM) and two sparsely granulated somatotroph (SG-SM) adenomas, Fo r demonstration of chromosome 11, the direct FISH technique was applie d on imprints from fresh adenoma tissue fixed in acetone using an a-sa tellite specific centromeric probe. The slides were studied with a flu orescence microscope and the percentages of positive nuclei with aberr ant fluorescent signals were counted. All tumors exhibited numerical c hromosomal abnormalities in 8-23% of their cell population and include d nuclei containing 1-3 extra chromosome 11 copies. The SG-SM adenomas exhibited more prominent abnormalities compared with the DG-SM adenom as. We conclude that numerical chromosome 11 abnormalities represent a frequent event among somatotroph adenomas with a tendency for higher frequency in SG-SM adenomas.