Chromosomal imbalances in some benign orbital tumours

PURPOSE: To examine benign orbital tumours for chromosomal imbalances. METHODS: Specimens obtained from orbital tumours were screened for chromosomal imbalances using high resolution comparative genomic hybridization (CGH). The imbalances detected by CGH were confirmed by using fluorescence in situ hybridization (FISH) and loss of heterozygosity (LOH) analysis. RESULTS: Chromosomal gains or losses were seen in 4/6 pleomorphic adenomas (gains at 8q; losses at 4p, 5p, 8p, 11p and 14q), 2/4 schwannomas (losses at 16p and 22q), and 1/9 cavernous haemangiomas (losses at 13q). Compared to previous studies of pleomorphic adenomas using G-band analysis, chromosomal imbalances were more frequently detected by using CGH. Gains of 8q11-q22 and losses of 4p15-pter, 11p12-p15, and 14q12-q23 in pleomorphic adenomas, losses of 16p12-p13 in schwannomas, and losses of 13q32-qter in cavernous haemangiomas have not been reported previously. CONCLUSIONS: A range of chromosomal imbalances was detected even within tumours of the same histological subtype. We did not observe common chromosomal gains or losses that were characteristic for orbital presentation of the tumours. The clinical relevance of the abnormalities is uncertain, but they may indicate the position of genes that could play a role in tumour development.