[Bilateral uveal melanomas. Five case reports]

Uveal malignant melanoma is the most common primary intraocular tumor in adults. The occurrence of bilateral uveal melanoma is an extremely rare event, but the observed frequency is nevertheless higher than what can be attributed to chance. Possible responsible factors may include a genetic predisposition.

This retrospective study investigated the charts of patients examined from July 1988 to July 2001. For each patient, the clinical characteristics of the tumor (diameter, thickness, location), treatments, and results were noted, as were the eye involved, the presence of ocular melanocytosis, cutaneous melanoma, and second primary cancers. The information was then subjected to statistical analysis.

Of 2 461 patients with unilateral primary uveal melanoma, five were identified as having bilateral uveal melanoma (0.2%). The expected number of cases would be less than one, hypothesizing an incidence of second melanoma identical to the incidence of a primary melanoma in the general population. The interval between the diagnosis of first and second primary uveal melanomas ranged from 0 to 6 years (median, 2 years). There was no clinical evidence of ocular melanocytosis in any of the five patients. The uveal melanoma was choroidal in three patients and affected the ciliary body or iris and choroid in two patients.

The discrepancy between the estimated incidence (thought by Shammas to be one case every 18 years) and the observed incidence of bilateral primary uveal melanoma could be the result of many possible factors. An increased incidence of unilateral uveal melanoma could be a cause but in fact the incidence of uveal melanoma seems stable. Uveal melanoma may have been misdiagnosed in earlier years. The presence of a genetic predisposition to uveal melanoma is a possible explanation (suspected because of bilateral cases, familial cases and association with other primary malignancies). Ocular melanocytosis, which is described as more common in patients with bilateral uveal melanoma, was not seen in our series.

Bilateral primary uveal melanoma occurs more frequently than expected. Unidentified germline mutations may be involved in pathogenesis. These cases serve as a reminder of the of the importance of careful examination of the second eye.