A 58-year-old Indian man undergoes routine fundoscopy during an annual eye examination. A flat, slate-gray pigmented lesion is noted at the posterior pole, measuring 4 mm in diameter. The structure marked **A** in the diagram shows this lesion with overlying drusen. Which of the following clinical findings would MOST strongly suggest that this lesion is a benign choroidal nevus rather than a choroidal melanoma?

Explanation

## Why "Presence of overlying drusen and absence of subretinal fluid" is right The structure marked **A** — a flat, slate-gray lesion with overlying drusen — is the classic presentation of a benign choroidal nevus. According to Shields et al. (2010 Zimmerman Lecture), overlying drusen are a sign of chronicity and strongly favor a benign nevus. The absence of subretinal fluid (one of the TFSOM risk factors for malignancy) further supports benignity. A nevus with zero to one risk factor carries only a 3–8% risk of growth at 5 years, whereas the presence of multiple TFSOM factors (thickness >2 mm, subretinal fluid, symptoms, orange pigment, margin near disc, ultrasonographic hollowness, absence of halo, absence of drusen) significantly elevates malignancy risk. Drusen are a protective finding indicating long-standing, stable disease. ## Why each distractor is wrong - **Elevated thickness greater than 2 mm with orange pigment**: Thickness >2 mm (T) and orange pigment (O) are two major TFSOM risk factors for malignant transformation. Orange pigment represents lipofuscin overlying the tumor and is associated with melanoma, not benign nevus. This combination strongly suggests melanoma risk. - **Subretinal fluid with symptoms of visual disturbance**: Subretinal fluid (F) and symptoms (S) are two additional TFSOM risk factors. Together with other factors, they substantially increase the likelihood of malignancy and warrant urgent referral to ocular oncology. - **Margin within 3 mm of the optic disc with acoustic hollowness on B-scan**: Margin proximity to the optic disc (M) and ultrasonographic hollowness (U) are TFSOM risk factors. Acoustic hollowness (low internal reflectivity) on B-scan is characteristic of melanoma and indicates high malignancy risk. **High-Yield:** Overlying drusen = chronicity = benign nevus; TFSOM mnemonic identifies risk factors for malignant transformation (T, F, S, O, M, U, H, HD). [cite: Shields CL et al. The 2010 Zimmerman Lecture (Arch Ophthalmol)]