Molecular cytogenetics of chromosome 11 in pituitary adenomas: A comparison of fluorescence in situ hybridization and DNA ploidy study

Chromosome 11 abnormalities were detected by fluorescence in situ hybridiza tion (FISH) technique and compared with DNA ploidy in 24 surgically removed pituitary adenomas. The tumors were diagnosed and classified by histology, electron microscopy, and pituitary hormone immunocytochemistry. They inclu ded 2 densely granulated somatotroph (DG-SM) and 4 sparsely granulated soma totroph (SG-SM) adenomas, 3 SG lactotroph (LT), 2 mixed somatotroph-lactotr oph (SM-LT), 4 functioning corticotroph (CRT), 1 silent CRT subtype I, 1 th yrotroph, 1 mixed thyrotroph-somatotroph, 2 gonadotrophs, and 4 null cell a denomas. FISH analysis with an alpha-satellite DNA probe specific for chrom osome II showed numerical abnormalities in 16 functioning (94%) and 5 nonfu nctioning (71%) adenomas. Ten functioning tumors showed aneuploid histogram s, whereas the remaining and all nonfunctioning adenomas were diploid. Aber rant chromosome 11 signals were noted mostly in aneuploid adenomas involvin g 17% to 100% of their cell population. The severity of chromosome ii aberr ations in adenomas containing extra copies often correlated with a higher D NA index (DI). Monosomy 11 as dominant aberration was noted in a mixed SM-L T and to a lesser degree in 3 CRT adenomas involving 21% to 97% of their ce ll population. Two of these CRT adenomas were associated with normal DI, wh ereas the remaining third showed a high DI, indicating increased copy numbe r of chromosomes other than of chromosome 11. In conclusion, chromosome 11 abnormalities are common in all types of pituitary adenomas, occurring more frequently in functioning tumors. Specific numerical abnormalities, such a s monosomy and trisomy, tend to be associated with certain adenoma types, w hereas tumors with extra chromosome 11 copies often exhibit aneuploid histo grams. Copyright (C) 1999 by W.B. Saunders Company.