Chromosomal alterations in iris melanoma

Purpose Melanomas arising in the iris (IM) are rare comprising about 5% of all uveal melanomas (UM). They are seldom lethal with only 2‐4% of IM associated with metastatic spread. The genetic pathogenesis of IM and its favourable outcome, compared with choroidal and ciliary body UMs, is still not well understood. The aim of this study was to investigate whether genetic changes associated with prognosis in choroidal/ciliary body UMs (i.e. monosomy 3 and polysomy 6p or 8q) are also indicative of prognosis in IM. Methods Changes in chromosome 1p, 3, 6 and 8 copy number were detected in seven IMs by Multiplex Ligation‐dependent Probe Amplification. Full clinical, histomorphological and survival information was available for each patient. Results There were five male and two female patients, whose age ranged from 32‐68 years (median 51 yrs). Three patients had received previous proton beam therapy. Two patients died due to metastatic melanoma; both tumours showed polysomy 8q, with one tumour also showing monosomy 3 and the other showing polysomy 6p. Time from diagnosis to metastatic death was longer for the patient with a polysomy 6p tumour (6 yrs) than for the monosomy 3 tumour (3 yrs). The remaining five patients demonstrated no consistent genetic alterations and were alive with no evidence of metastases at the time of analysis. Conclusion This study suggests that genetic changes in chromosomes 3, 6p and 8q, previously observed for choroidal/ciliary body UM, could also be associated with survival in IMs. Further high‐resolution studies with a larger cohort of IM are currently being performed to validate these data.