Genetic aspects of uveal melanoma

Familial uveal melanoma: a report on two families and a review of the literature

PURPOSE

A total of 69 families affected by uveal melanoma have been reported in the literature. This report describes two additional families. In addition to presenting these cases, which constitute exceptions, the paper reviews the literature.

MATERIAL AND METHODS

Two families, each with two affected members, were analysed in this retrospective study. The pedigree of each family has been pieced together.

RESULTS

Considering the low incidence of familial uveal melanoma in the general population, it seems unlikely that inherited genetic factors are responsible for the condition; this question remains difficult to resolve.

DISCUSSION

The characteristics of each family history are described and compared with the literature data. The mode of possible inheritance is discussed. Both the histopathology and anatomical location are studied, after which we discuss the body of evidence to establish whether there is an inherited cancer predisposition syndrome in patients with familial uveal melanoma.

CONCLUSION

The statistical likelihood of such an uncommon tumour occurring independently in two or more family members leads us to believe that some cases of familial uveal melanoma may go unrecognized, and that reports on too few families have been published worldwide to prove the existence of a single mendelien gene. However, appropriate tissue samples, such as blood and tumour samples, should be obtained and conserved for present or future cytogenetic and molecular genetic studies.

Bilateral uveal melanoma: a series of four cases

AIM

To describe the occurrence of bilateral primary choroidal melanoma in four patients.

METHODS

All patients attending the Liverpool Ocular Oncology Centre with uveal melanoma between January 1993 and February 2002 were identified, and those with bilateral primary choroidal melanoma were reviewed. Their presentation and management are described.

RESULTS

Four patients, all female, were identified. Patient 1 presented with a right juxtapapillary melanoma at the age of 64, which was treated with krypton laser and endoresection, and then when aged 73 required proton beam radiotherapy for a melanoma in her left eye. Patient 2 presented at the age of 82 with bilateral choroidal melanomas and underwent simultaneous bilateral plaque radiotherapy. Patient 3 presented with bilateral choroidal melanomas at the age of 75 and was treated initially with bilateral proton beam radiotherapy. Patient 4 was treated at the age of 54 with right plaque radiotherapy for a choroidal melanoma, and 3 years later needed plaque radiotherapy for a melanoma in her other eye.

CONCLUSION

Bilateral choroidal melanoma is possible and should be a consideration in the continuing management of patients with choroidal melanoma.

Frequent loss of heterozygosity on chromosome 6p in uveal melanoma

Lack of expression of HLA class I antigens is frequently observed on primary uveal melanoma, and is correlated with improved patient survival. Several mechanisms may contribute to the observed loss of HLA class I expression, including changes at the DNA level. In this study, we used microsatellite analysis as a molecular genetic approach to examine loci on chromosome 6p for loss of heterozygosity (LOH). Three pairs of microsatellite markers were used to screen 20 formalin-fixed, paraffin-embedded uveal melanomas for LOH on the short arm of chromosome 6. In all cases, normal adjacent scleral tissue was used as a control. We identified LOH in eleven cases from microsatellite locus D6S105 to the telomere, in eight cases from microsatellite locus D6STNFa to the telomere (area includes D6S105), and in seven cases from microsatellite locus D6S291 to the end of chromosome 6p (includes D6STNFa and D6S105). In seven cases, retention of heterozygosity was found at all three loci using these primers. Our results suggest that loss of heterozygosity on chromosome 6p is a common feature in uveal melanoma. We did not find a correlation between the presence of LOH and locus-specific HLA-A and -B expression.

Genetic predisposition to ocular melanoma

Uveal melanoma is the most common primary intraocular malignancy, with an annual incidence of 6 per million. The environmental factors known to increase the risk of cutaneous melanoma appear to be less important in ocular melanoma and it is conceivable that host factors have a greater impact. The coexistence of ocular and cutaneous melanoma in some patients suggests a predisposition to both types and implicates mutations in the CDKN2A gene in a proportion of these cases. An association between ocular melanoma and breast and/or ovarian cancer has also been reported and recent studies of breast cancer families strongly implicate BRCA2 as a predisposition gene. Other more common genes predisposing to ocular melanoma may be of low penetrance. An example of a gene in this class is MC1R, which affects host response to ultraviolet radiation. Identification of genes conferring an increased risk of ocular melanoma should provide insights into the pathogenesis of this tumour. Furthermore, it offers an opportunity to identify individuals at a high risk who may benefit from targeted surveillance. At present the identification of such individuals is restricted to the small number belonging to BRCA2 families and those with the atypical mole syndrome.

Bilateral primary uveal melanoma. Bad luck or bad genes?

BACKGROUND

The occurrence of bilateral primary uveal melanoma has been assumed to be a rare, random event . Bilaterality of a primary cancer is suggestive of an inherited cancer predisposition. The authors therefore evaluated patients with bilateral primary uveal melanoma for such cancer predisposition.

METHODS

The charts of 4500 patients with uveal melanoma were reviewed for the presence of bilaterality. The clinical profile of patients with bilateral primary uveal melanoma was studied. The presence of ocular melanocytosis, familial atypical mole and melanoma syndrome, neurofibromatosis type 1, cutaneous melanoma, familial uveal melanoma, Li-Fraumeni syndrome, and second primary cancers also was investigated.

RESULTS

Of 4500 patients with primary uveal melanoma, 8 (0.18%) were identified to have bilateral primary uveal melanoma. Using the annual incidence rate (Shammas and Watzke) and normal approximation to the binomial, the expected number of patients with primary bilateral uveal melanoma in the authors' series was calculated to be less than one person. Observation of eight patients with bilateral primary uveal melanoma represented greater than expected occurrence (P<0.0001). The mean age at diagnosis in the first eye was 56 years. The interval between the diagnosis of uveal melanoma in the two eyes ranged from 2 to 32 years (median, 10.5 years). Two patients had bilateral ocular melanocytosis. Ocular melanocytosis was more common (2/8, 25%) in patients with bilateral uveal melanoma compared with those with unilateral uveal melanoma (60/4492, 1.3%). This difference was statistically significant (P = 0.001). No relation to familial atypical mole and melanoma syndrome, cutaneous melanoma, neurofibromatosis type 1, familial uveal melanoma, second primary cancers, or Li-Fraumenni syndrome was observed.

CONCLUSIONS

Bilateral primary uveal melanoma occurs more frequently than expected by chance, and may be associated with ocular melanocytosis. In the authors' series, there was no clinical evidence of an inherited genetic predisposition for bilateral primary uveal melanoma. Unidentified germ-line mutations may be involved in pathogenesis of bilateral uveal melanoma.