Bilateral primary uveal melanoma. Bad luck or bad genes?

Abstract

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.