Unsuspected and misdiagnosed posterior uveal melanoma following enucleation and evisceration in Ottawa-Gatineau.

ABSTRACT

OBJECTIVE: There is a gap in the recent literature on the topic of clinically misdiagnosed and unsuspected posterior uveal melanomas (PUM) with a calculation of the frequency of these events for a specific geographical area. As the only ophthalmic pathology laboratory in our region, we determined the rate of these outcomes over a 16-year period. METHODS: We retrospectively reviewed 2558 consecutive ophthalmic pathologic specimens in the Ottawa-Gatineau region, of which 334 were eviscerations and 227 were enucleations. We calculated the frequency of clinically misdiagnosed PUM and of clinically unsuspected PUM. We also determined the rate of uveal melanoma undergoing enucleation. RESULTS: From 100 diagnoses of PUM, 2 (2.0%) cases were clinically unsuspected and 2 (2.0%) cases were clinically misdiagnosed. The rate of uveal melanoma undergoing enucleation was 5.6 cases per 1 000 000 of population per annum. From 2009 to 2012, the incidence of this event was 3.8 cases per 1 000 000 per annum, which was lower than the previous three 4-year increments. CONCLUSIONS: We present the first and only single-centred, population-based data on the rates of unsuspected PUM and of clinical misdiagnosis of PUM in the era of modern diagnostic imaging. Our rate of clinical misdiagnosis is within the range of recent reports of this event. Unsuspected PUM occurred at a rate substantially lower than previously published. The incidence of uveal melanoma undergoing enucleation has decreased despite an increase in population, which reflects a shift in management from enucleation to radiation therapy.