A 50-year-old man presents with a painless, amelanotic, rapidly growing raised choroidal lesion. B-scan ultrasonography shows a dome-shaped choroidal lesion with internal acoustic hollowness. Orbital MRI shows T1 hyperintensity and T2 hypointensity. The MOST likely diagnosis based on MRI characteristics is:

• A Choroidal osteoma (ossified lesion with calcium signal)
• B Choroidal metastasis (T1 hypointense, T2 hyperintense — bright on T2)
• C Choroidal hemangioma (T1 isointense, T2 hyperintense)
• D Uveal melanoma (T1 hyperintense, T2 hypointense due to melanin and blood products) ✓

Explanation

Uveal melanoma has characteristic MRI signal: T1-weighted HYPERINTENSE (high signal — due to melanin shortening T1 relaxation time and paramagnetic properties) and T2-weighted HYPOINTENSE (low signal — due to melanin T2 shortening). This MRI signature is pathognomonic for melanin-containing melanoma. Choroidal metastasis typically appears T1 hypointense and T2 hyperintense (bright). Choroidal hemangioma is T1 isointense to bright and T2 hyperintense. B-scan showing acoustic hollowness with choroidal excavation (double-layer sign) further supports melanoma.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.