[Transformation of choroidal nevus into melanoma]

The risk of choroidal melanoma developing from choroidal nevus (CN) varies in range of 0.78-7%. Absence of a common terminology and distinct diagnostic criteria characterizing small melanoma de novo and unusual CN often complicates treatment choice and patient prognosis.

To study the clinical features and the role of visualization methods in the diagnosis of CN transformation into melanoma.

The study analyzes the clinical picture and visualization results of 11 patients with initial diagnosis of «choroidal nevus» (n=3) and «suspicious choroidal nevus» (n=8).

Examination and continued observation revealed 7 patients to have melanoma that had developed from CN (2 of them confirmed with histological studies). The time before CN transformed into melanoma varied between 4 and 13 years, with median 5 [4; 12] years. Two patients were diagnosed with primary melanoma (melanoma de novo), two other patients - with suspicious CN. In progressive CN transforming into melanoma, visual impairments occurred between 6 months and 13 years in 6 out of 7 patients. Initial prominence of suspicious CN at the first visit was 1.9±0.68 mm (0.9 mm to 2.67 mm). The characteristic features of suspicious CN transforming into initial melanoma are: 1) asymmetric shape of the edges of expanded choroidal complex; 2) presence of areas of damaged choriocapillaris layer, direct and indirect signs of loss of integrity of the Bruch's membrane; 3) areas of accumulation of moderately hyperreflective subretinal exudate; 4) presence of intraretinal hyperreflective inclusions. The signs distinguishing primary choroidal melanoma from melanoma that had developed from CN are: 1) absence of areas with tomography pattern characteristic of nevi; 2) more pronounced asymmetry of the shape of edges, compared to melanoma developed from CN; 3) presence of cysts in larger tumors, compared to melanoma developed from CN.

All patients with CN should be regularly followed up by an ophthalmologist.