Presumed incipient choroidal melanoma: proposed diagnostic criteria and management.

Abstract

To propose diagnostic criteria for a presumed incipient choroidal melanoma based on tumour growth rate and tumour doubling time (TDT) and to describe management of such tumours with transpupillary thermotherapy (TTT). Retrospective interventional case series of nine consecutive presumed incipient uveal melanomas diagnosed and treated with TTT in 2010-2017. Growth rate in mm/year and per cent/year in largest basal diameter (LBD) and TDT were compared with published data for uveal melanomas and growing naevi that did not transform to melanoma under long-term follow-up. The median LBD and thickness were 1.6 mm (range 0.9-2.3) and 0.20 mm (range 0.15-0.29), respectively. The median age was 57 years (range 47-78). Seven tumours were classified as de novo melanomas and two as transformed naevi. The median time from first observation to diagnosis was 3.3 years (range 2.2-7.3), LBD growth rate 0.25 mm/year (range 0.11-0.72) and 34 per cent/year (range 10-1437), and TDT 609 days (range 97-1612). The estimates matched those reported for uveal melanoma (median TDT 521 days, 90th percentile 2192) and exceeded those for growing naevi (median growth rate 0.04 mm/year, 90th percentile 0.12; 1.1 per cent/year, 90th percentile 2.6). The predicted median age at de novo appearance was 51 years (range 32-63). No tumour grew after TTT during a median follow-up of 2.1 years (range 0.6-8.7). In this series, relative growth rate and TDT best qualified as diagnostic criteria for an incipient choroidal melanoma. Too small for brachytherapy, they could be managed with TTT.