How should choroidal melanoma be evaluated and managed, including recommended imaging, referral to an ocular oncologist, and treatment options based on lesion size?

Choroidal Melanoma: Evaluation and Management

All patients with suspected choroidal melanoma require immediate referral to an ocular oncologist for definitive diagnosis and treatment planning, with management decisions based on tumor size, growth characteristics, and specific risk factors identified through multimodal imaging.

Initial Evaluation and Risk Stratification

Clinical Assessment and Imaging

When evaluating a pigmented choroidal lesion, utilize the TFSOM-DIM mnemonic to identify risk factors for malignancy 1:

• Thickness >2 mm (by ultrasonography)
• Fluid subretinal (by optical coherence tomography)
• Symptoms of vision loss (by Snellen acuity)
• Orange pigment (by autofluorescence - lipofuscin indicating aggressive tumor) 2, 1
• Melanoma hollow (by ultrasonography)
• DIaMeter >5 mm (by photography)

Multimodal imaging is essential and should include 1, 3:

• Color fundus photography
• B-scan ultrasonography for tumor dimensions and elevation
• Optical coherence tomography (OCT) for subretinal fluid detection
• Fundus autofluorescence for orange pigment identification
• Transillumination to assess tumor shadow and dimensions 4

Risk-Based Transformation Rates

The probability of nevus transformation to melanoma at 5 years correlates directly with the number of TFSOM-DIM risk factors present 1:

• 0 factors: 1.1%
• 1 factor: 11%
• 2 factors: 22%
• 3 factors: 34%
• 4 factors: 51%
• 5 factors: 55%

Management Algorithm by Tumor Size

Small Choroidal Melanoma (<3 mm thickness)

For lesions <3 mm thick with documented growth or ≥2 TFSOM-DIM risk factors, active treatment should be initiated 4, 5. Small melanomas without documented growth can be observed with serial imaging every 3-6 months, but true growth must be confirmed with serial photographs, ultrasound, and transillumination before deferring treatment 4.

Treatment options for small melanoma include:

• Iodine-125 episcleral plaque brachytherapy (preferred for tumors 1.0-5.0 mm height, ≤16 mm basal diameter) 5:

  • 5-year local control: 98%
  • 5-year metastasis-free survival: 87.5%
  • Vision preservation (≥20/50) at 3 years: 56%
  • Significantly lower radiation doses to lens, optic disc, and fovea compared to older protocols 5

• AU-011 nanoparticle therapy (investigational infrared dye-conjugated virus-like nanoparticle) - currently in clinical trials with goal of tumor regression while minimizing vision loss 1

Medium Choroidal Melanoma (3-5 mm thickness)

Medium melanomas require active treatment with plaque radiotherapy 5. Using American Brachytherapy Society (ABS) guidelines rather than older COMS protocol reduces radiation toxicity:

• Mean dose reduction: 34% to lens, 39.4% to optic disc, 41.4% to fovea
• 5-year local control: 98%
• 5-year overall survival: 95%
• 5-year metastasis-free survival: 87.5% 5

Large Choroidal Melanoma (>5 mm thickness)

Large melanomas typically require enucleation or consideration of neoadjuvant therapy, though specific treatment decisions should be made by the ocular oncologist based on tumor location, patient factors, and metastatic risk assessment 2.

Critical Pathologic Features for Prognostication

When tissue is obtained, the following features must be documented 2:

Essential tumor characteristics:

• Location (choroid only, choroid and ciliary body, ciliary body only, iris involvement)
• Dimensions: maximum zone of scleral contact, perpendicular dimension, elevation from sclera interface
• Cell type (McLean's modification of Callender classification)
• Mitotic figures per 40 high-power fields
• Presence of tumor-infiltrating lymphocytes (≥100 per 20 HPF)
• Extraocular extension or intrascleral emissary channel involvement

Prognostic molecular markers:

• Cytogenetic abnormalities, especially chromosomes 3 and 8 2
• Nucleolar diameter measurements
• Microvascular density patterns 2

Surveillance and Metastatic Screening

For confirmed choroidal melanoma, systemic imaging is warranted given metastatic potential 2:

• MRI of head and orbits with and without IV contrast is the most useful modality for evaluating intraocular masses, retrolaminar optic nerve involvement, choroid-scleral infiltration, orbital invasion, and intracranial spread 2

• CT with IV contrast can be used as an alternative, particularly for detecting calcification and evaluating extraocular extension 2

Post-treatment surveillance should follow risk-stratified protocols, with higher-risk tumors (>3 mm thickness, adverse pathologic features) requiring more intensive monitoring for both local recurrence and systemic metastasis 2.

Common Pitfalls to Avoid

Do not delay referral for lesions with any TFSOM-DIM risk factors - the 5-year transformation rate exceeds 10% with even a single risk factor 1.

Do not rely on clinical appearance alone - orange pigment (lipofuscin) visible on autofluorescence is considered evidence of an aggressive tumor and mandates urgent evaluation 2.

Do not assume stability means benignity - documented growth is the definitive trigger for treatment, requiring serial multimodal imaging rather than single-time-point assessment 4.

Avoid under-staging - transillumination and B-scan ultrasonography are essential for accurate tumor dimension measurement, as clinical appearance can underestimate true tumor thickness 2.