Most choroidal naevi are harmless, but clinicians become more concerned when a lesion shows validated features linked to growth into melanoma. A practical evidence-based checklist used in ocular oncology is TFSOM-DIM, which captures key “activity” signs: ¹
- Thickness > 2 mm
- Fluid (subretinal fluid on optical coherence tomography)
- Symptoms (new blur/distortion/scotoma)
- Orange pigment (lipofuscin on autofluorescence)
- Margin near the optic disc
- Diagnosed hollowness (low internal reflectivity on ultrasound)
- I/M: Imaging evidence of suspicious change, and absence of protective chronicity signs such as drusen/halo (depending on the model used)
The clinical point is not “a naevus is dangerous because it exists”, but: risk rises as objective factors accumulate. Large series show that documented growth is uncommon overall, but the probability increases sharply with multiple risk factors. ¹ ³
Good practice is to measure, not “reassure”: baseline photos, OCT and (when needed) ultrasound, then follow-up based on the lesion’s risk profile. ²
References
- Shields CL, Furuta M, Berman EL, Zahler JD, Hoberman DM, Dinh DH, et al. Choroidal nevus transformation into melanoma: analysis of 2514 consecutive cases. Archives of Ophthalmology. 2009;127(8):981-987. doi:10.1001/archophthalmol.2009.151. PMID: 19667334.
- Dalvin LA, Shields CL, Ancona-Lezama DA, Yu MD, Di Nicola M, Williams BK Jr, et al. Combination of multimodal imaging features predictive of choroidal nevus transformation into melanoma. British Journal of Ophthalmology. 2019;103(10):1441-1447. doi:10.1136/bjophthalmol-2018-312967. PMID: 30523045.
- Singh AD, Kalyani P, Topham A. Estimating the risk of malignant transformation of a choroidal nevus. Ophthalmology. 2005;112(10):1784-1789. doi:10.1016/j.ophtha.2005.06.011. PMID: 16154197.
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