What is a choroidal nevus (benign tumor) of the eye?

Choroidal Nevus: A Benign Melanocytic Tumor of the Eye

A choroidal nevus is a benign melanocytic tumor of the eye found in approximately 5-8% of the adult population, appearing as a well-circumscribed, typically pigmented lesion in the choroid layer that is generally flat or slightly elevated and stable in size over time. 1

Clinical Characteristics

Appearance and Prevalence

• Found in approximately 5-8% of adults, more common in white individuals 1
• More frequently observed in women (71.25%) than men 2
• Typically round (73.8%) or oval (26.2%) in shape 2
• Average size of approximately 1.25 mm in diameter 3
• Can be pigmented or occasionally amelanotic (non-pigmented) 4
• Most commonly located in the juxtapapillary (11.9%) and macular (29.76%) regions 2

Associated Features

• Often accompanied by overlying retinal pigment epithelial alterations including:
  • Drusen (61%) - most common feature
  • Retinal pigment epithelial atrophy (6%)
  • Retinal pigment epithelial hyperplasia (10%)
  • Fibrous metaplasia (6%) 5
• May occasionally present with subretinal fluid (5%) 5
• Orange pigment may be present in some cases (6%) 5

Diagnostic Evaluation

A comprehensive evaluation of choroidal nevus should include:

1. Slit lamp examination
2. Fundus photography
3. Ocular ultrasound
4. Optical coherence tomography (OCT)
5. Fluorescein angiography (if neovascularization is suspected) 1

Risk of Malignant Transformation

The risk of transformation from nevus to melanoma is small, estimated at less than 1% overall 3. Risk factors for malignant transformation can be recalled using the mnemonic "To find small ocular melanoma using helpful hints daily":

• Thickness greater than 2 mm
• Subretinal Fluid
• Symptoms (flashes, floaters, blurred vision)
• Orange lipofuscin pigment
• Margin less than 3 mm from optic disk
• Ultrasonographic Hollowness
• Halo absence
• Drusen absence 3

The presence of three or more risk factors implies more than a 50% chance for transformation to melanoma within 5 years 1, 3.

Management Approach

Observation

• Standard management for typical choroidal nevus is observation 1
• Follow-up frequency:
  • Annual for low-risk lesions
  • Every 3-6 months for lesions with suspicious characteristics 1

Documentation

Each follow-up visit should document:

• Changes in size and thickness
• Changes in associated drusen
• Appearance of new risk factors 1

Growth Patterns

• 31% of choroidal nevi may show slight enlargement over long-term follow-up (mean 15 years) without malignant transformation 5
• The median rate of enlargement is approximately 0.06 mm/year 5
• Younger patients (under 40 years) show higher frequency of enlargement (54%) compared to older patients (19% in those over 60) 5

When to Refer to Ocular Oncology

Referral is recommended if:

• Documented growth occurs
• Multiple risk factors appear
• Changes in appearance suggest transformation 1

Treatment Considerations

• Typical choroidal nevi require only observation
• If transformation to melanoma occurs, treatment options include:
  • Brachytherapy
  • Proton therapy
  • Enucleation (in advanced cases)
• For secondary complications:
  • Anti-VEGF intravitreal injections for choroidal neovascularization
  • Photodynamic therapy for serous retinal detachment without neovascularization 6

Patient Education

Patients should be informed about:

• The benign nature of typical choroidal nevi
• The importance of regular follow-up
• Warning signs requiring immediate evaluation:
  • Decreased vision
  • Visual distortion
  • New floaters
  • Flashes of light 1

By understanding the clinical features and appropriate management of choroidal nevi, clinicians can effectively monitor these common benign lesions while remaining vigilant for signs of malignant transformation.