What is the main differential diagnosis of a relatively flat pigmented fundus lesion?

• 1.
  

  Choroidal nevus ( Fig. 50-1 )

  
  

  
  

  
  

  

  
  

  
  

  Typical choroidal nevus adjacent to the optic disc.

  
  
  
  
• 2.
  

  Congenital hypertrophy of the retinal pigment epithelium (CHRPE) ( Fig. 50-2 )

  
  

  
  

  
  

  

  
  

  
  

  Congenital hypertrophy of the retinal pigment epithelium.

  
  
  
  
• 3.
  

  Combined hamartoma

What ophthalmoscopic features help to differentiate choroidal nevus, CHRPE, and combined hamartoma?

Choroidal nevus is generally a slate-gray lesion with a slightly ill-defined border. Drusen may be present on the surface of the lesion. CHRPE is usually black, has a sharply demarcated border, and may have depigmented lacunae through which the underlying choroid can be visualized. Combined hamartoma shows vitreoretinal traction that is not seen with the other two conditions.

Do both choroidal nevus and CHRPE have malignant potential?

Although both lesions are benign and usually stationary, nevus can give rise to melanoma and most melanomas probably arise from a preexisting nevus. CHRPE was once believed to be stationary with no malignant potential. However, it has recently been recognized to show enlargement in diameter in 80% of cases and to rarely become elevated and evolve into adenocarcinoma of the retinal pigment epithelium.

What is the main differential diagnosis of an elevated pigmented fundus lesion?

• 1.
  

  Choroidal melanoma

  
  
• 2.
  

  Subretinal hemorrhage

  
  
• 3.
  

  Tumor of the retinal pigment epithelium

  
  
• 4.
  

  Bilateral diffuse uveal melanocytic proliferation

What ophthalmoscopic features help to differentiate a choroidal melanoma from a subretinal hemorrhage?

Choroidal melanoma usually is a rather homogeneous brown-to-black lesion with a smooth surface. Subretinal hemorrhage in the macular area (age-related macular degeneration) or in the peripheral fundus (peripheral disciform degeneration) initially has a reddish-blue color; because it undergoes resolution, it has a more heterogeneous color with areas of fresh red blood and older yellow blood.

What is the most practical ancillary test for differentiating choroidal melanoma from subretinal blood?

The most practical test is fluorescein angiography. Most melanomas show hyperfluorescence, and most hemorrhages are hypofluorescent.

What is the significance of a mushroom-shaped fundus lesion?

A mushroom-shaped fundus lesion is strongly suggestive of choroidal melanoma ( Fig. 50-3 ). Even when the mushroom-shaped lesion is nonpigmented, melanoma is still the most likely diagnosis. It is very unusual for other fundus lesions to assume a mushroom shape.

Mushroom-shaped choroidal melanoma.

What is the best way to diagnose choroidal melanoma?

The best way is the use of binocular indirect ophthalmoscopy by an experienced ophthalmologist who is familiar with the characteristic features of choroidal melanoma and other lesions that simulate choroidal melanoma. Most melanomas can be readily diagnosed by indirect ophthalmoscopy alone. However, ancillary studies such as fluorescein angiography and ultrasonography are also quite reliable.

When the diagnosis is uncertain after ophthalmoscopy, what are the four most helpful ancillary tests in the diagnosis of uveal melanoma?

• 1.
  

  Transillumination

  
  
• 2.
  

  Fluorescein angiography

  
  
• 3.
  

  Ultrasonography

  
  
• 4.
  

  Fine-needle aspiration biopsy

Most melanomas cast a shadow with transillumination, are hyperfluorescent with angiography, and show low internal reflectivity with ultrasonography. Most simulating lesions show different patterns with these modalities. Fine-needle aspiration biopsy is perhaps the most reliable method, but it is an invasive procedure that requires a skilled and experienced physician.

What clinical signs suggest that a benign choroidal nevus is likely to grow and eventually evolve into a malignant choroidal melanoma?

Elevation of the lesion, orange pigment on the surface of the lesion, secondary retinal detachment, proximity of the lesion to the optic disc, and presence of visual symptoms.