Chromosomal aberrations in iris melanomas

BACKGROUND: Uveal melanomas can develop in the choroid, ciliary body and iris. In choroidal and ciliary body melanomas, specific chromosomal changes correlate with metastatic disease. Iris melanomas have a better prognosis than choroidal melanomas, and it would be interesting to know if they share chromosomal changes. In addition, iris melanomas might harbour UV-induced mutations of tumour suppressor genes, such as PTEN and CDKN2A.

METHODS: Twenty iris melanomas were analysed for chromosome 1p, 3, 6, 8, 9p and 10q abnormalities using fluorescence in situ hybridisation. These results were correlated to clinical follow-up data using statistical analyses.

RESULTS: (Partial) loss of chromosome 3 was observed in nine iris melanomas, and gain of 8q was present in seven tumours. Loss of chromosome 9p was demonstrated in seven tumours, but no deletions of the PTEN region on chromosome 10 were found. Three patients died of metastatic disease, and one patient developed liver metastases, but is still alive. Univariate analysis indicated a lower disease-free survival for patients with diffuse growing melanomas (p=0.01), melanomas that lost a copy of chromosome 3 (p=0.03), or invading the ciliary body (p=0.01). In a multivariate analysis, none of the correlations were significant.

CONCLUSION: Loss of chromosome 3 as well as loss of chromosomal region 9p21 (that entails tumour suppressor gene CDKN2A) plays a role in iris melanoma. A firm correlation with disease-free survival could not be established, possibly due to the small sample size.