Presumed incipient choroidal melanoma: proposed diagnostic criteria and management.

Aims: 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).

Methods: 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.

Results: 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).

Conclusions: 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.