Uveal melanoma

Uveal melanoma is the most common primary malignant tumor of the eye. It develops from choroidal melanocytes and is therefore often pigmented. The tumor can arise from the choroid, iris, or ciliary body. Symptoms, which depend on the location of the tumor, begin when the tumor extends to the optical axis or if there is concomitant retinal detachment or interference with the function of the ciliary body or pupil. The condition is diagnosed through fundoscopy and ultrasonography. Treatment usually consists of radiation therapy or surgical removal of the tumor in advanced disease. With the exception of iris melanoma, uveal melanoma is typically diagnosed late because of the lack of early symptoms. Approximately half of patients go on to develop distant metastases via hematogenous spread, most commonly to the liver, which are then fatal.

• Incidence: 6–10/1,000,000 per year
• Peak incidence: 50–70 years
• Race: More common in individuals of Northern European descent and those with light eye and/or skin color
• Location
  • Choroid: ∼ 80%
  • Ciliary body: ∼ 15%
  • Iris: ∼ 5%

References:^[1][2]

Epidemiological data refers to the US, unless otherwise specified.

• Etiology unclear
• Risk factors
  • Congenital ocular/oculodermal melanocytosis and uveal nevus
  • Light skin color
  • Light color of the iris
  • Choroidal nevus
  • Iris nevus
  • Cutaneous nevus

References:^[3]

Symptoms vary depending on melanoma location.

• Choroid or ciliary body melanoma
  • Initially asymptomatic
  • Late symptoms
    • Vision loss due to tumor growth into the optical axis
    • Visual field defects, floaters, and/or photopsia due to tumor-related retinal detachment
    • Blurred vision due to tumor growth in the ciliary body
• Iris melanoma
  • Typically discovered earlier than choroidal or ciliary body melanoma because of visible signs
    • Distortion of pupil shape
    • A new brown nodule on the iris that becomes visible, or growth of a previous nodule
  • Blurred vision
• Transscleral melanoma with extension into the orbit
  • Pain
  • Vision loss
  • Cataract
  • Proptosis

• Fundoscopy
  • Nodular, dome-shaped subretinal mass
  • Traits that are more likely to be found in melanomas than benign nevi :
    • Tumor growth
    • Thickness > 2 mm
    • Orange-colored pigment on the surface of the lesion
    • Retinal detachment
• Additional tests
  • Ultrasonography
  • Fluorescein angiography
• Staging
  • Liver function tests
  • CT/MRI
  • Chest x-ray

References:^[4]

• Cytology
  • Spindle-shaped cells: best prognosis
    • Type A: thin nucleus and no visible nucleoli
    • Type B: large nucleus and visible nucleoli
  • Epithelioid melanoma (poor prognosis): large polygonal cells and prominent nucleoli
  • Intermediate cells: similar to epithelioid cells, but smaller
• Histopathology
  • Mixed-cell melanoma, which includes variable proportions of the three cell types, is the most common form.
  • Tumor cells with a bundle-like arrangement, which may have brown intracellular melanin in some areas

• Uveal metastases (mainly lung and breast cancer, lymphoma) are more common than primary uveal malignant melanoma.
• Choroidal nevus
• Retinal pigment epithelial hypertrophy
• Optic disc melanocytoma
• Hemangioma

The differential diagnoses listed here are not exhaustive.

• Observation: for small, asymptomatic tumors
• Radiation therapy
  • Brachytherapy
    • Iodine-125 (gamma rays)
    • Ruthenium-106 (beta rays)
  • Charged-particle radiation therapy
    • Indicated in circumpapillary lesions (i.e., lesions encircling the optic nerve)
• Enucleation : in advanced findings

References:^[1]

• Metastasis: hematogenous spread to liver, lungs, bones
• Retinal detachment
• Angle-closure glaucoma may develop as a consequence of blockage of the trabecular meshwork by the tumor, neovascularization, and/or pigment-laden macrophages.
• Complications of radiation therapy
  • Cataract
  • Radiation retinopathy
  • Optic neuropathy

We list the most important complications. The selection is not exhaustive.

• Iris melanoma → earlier detection → better prognosis than choroid or ciliary body melanoma
• As with melanoma, tumor thickness is an important negative prognostic factor.
• Only ∼ 3% of patients have metastases at diagnosis
• ∼ 50% develop metastases later in the course of their disease → ∼ 80% of those with metastases die within 1 year
• Histological tumor type associated with poor prognosis: epithelioid cell type

References:^[3]