Melanoma of the uveal tract (iris, ciliary body, and choroid), though rare, is the most common primary intraocular malignancy in adults. The mean age-adjusted incidence of uveal melanoma in the United States is approximately 4.3 new cases per million population.[1] The age-adjusted incidence of this cancer has remained stable for the past 50 years.

Uveal melanoma is diagnosed mostly at older ages, with a progressively rising age-specific incidence rate that peaks near the age of 70.[1] Host susceptibility factors associated with the development of this cancer include Caucasian race, light eye color, fair skin color, and the ability to tan.[1,2] In view of these susceptibility factors, numerous observational studies have attempted to explore the relationship between sunlight exposure and risk of uveal melanoma. To date, these studies have found only weak associations or yielded contradictory results.[1] Similarly, there is no consistent evidence that occupational exposure to UV light or other agents is a risk factor for uveal melanoma.[1]

Uveal melanomas can arise in the anterior (iris) or the posterior (ciliary body or choroid) uveal tract. Iris melanomas have the best prognosis, whereas melanomas of the ciliary body have the worst. Most uveal tract melanomas originate in the choroid. The ciliary body is less commonly a site of origin, and the iris is the least common. The comparatively low incidence of iris melanomas has been attributed to the characteristic features of these tumors, i.e., they tend to be small, slow growing, and relatively dormant in comparison with their posterior counterparts. Iris melanomas rarely metastasize.[3] Melanomas of the posterior uveal tract are cytologically more malignant, detected later, and metastasize more frequently than iris melanomas. The typical choroidal melanoma is a brown, elevated, dome-shaped subretinal mass. The degree of pigmentation ranges from dark brown to totally amelanotic.

Most uveal melanomas are initially completely asymptomatic. As the tumor enlarges, it may cause distortion of the pupil (iris melanoma), blurred vision (ciliary body melanoma), or markedly decreased visual acuity caused by secondary retinal detachment (choroidal melanoma). Serous detachment of the retina frequently complicates tumor growth. If extensive retinal detachment occurs, secondary angle-closure glaucoma occasionally develops. Clinically, several lesions simulate uveal melanoma, including metastatic carcinoma, posterior scleritis, and benign tumors, such as nevi and hemangiomas.[4]

Careful examination by an experienced clinician remains the most important test to establish the presence of intraocular melanoma. Ancillary diagnostic testing, including fluorescein angiography and ultrasonography, can be extremely valuable in establishing and/or confirming the diagnosis.[5]

A number of factors influence prognosis. The most important are cell type, tumor size, location of the anterior margin of the tumor, the degree of ciliary body involvement, and extraocular extension. Cell type, however, remains the most often used predictor of outcome.[6] The selection of treatment depends on the site of origin (choroid, ciliary body, or iris), the size and location of the lesion, the age of the patient, and whether extraocular invasion, recurrence, or metastasis has occurred. Extraocular extension, recurrence, and metastasis are associated with an extremely poor prognosis, and long-term survival cannot be expected.[7] The 5-year mortality rate caused by metastasis from ciliary body or choroidal melanoma is approximately 30%, compared with a rate of 2% to 3% for iris melanomas.[8] In a group of patients with large tumors of the choroid or choroid and ciliary body, the concurrent presence of abnormalities in chromosomes 3 and 8 was also associated with a poor outcome.[9]

In the past, enucleation (eye removal) was the accepted standard treatment for primary choroidal melanoma, and it remains the most commonly used treatment for large tumors. Because of the effect of enucleation on the appearance of the patient, the diagnostic uncertainty encountered by the ophthalmologist (particularly in the case of smaller tumors), and the potential for tumor spread, alternative treatments, such as radiation therapy (i.e., brachytherapy or external-beam, charged-particle radiation therapy), transpupillary thermotherapy, photocoagulation, and cryotherapy have been developed in an attempt to spare the affected eye and possibly retain useful vision.[10,11] One of the clinical trials of the randomized Collaborative Ocular Melanoma Study compared iodine 125 (¹²⁵I) episcleral-plaque brachytherapy to enucleation in treating patients with medium-sized choroidal tumors.[12] Eighty-five percent of the patients treated with ¹²⁵I brachytherapy retained their eye for 5 years or more, and 37% had visual acuity better than 20/200 in the irradiated eye 5 years after treatment.[12] No significant differences in mortality were observed between the two study arms after 12 years of follow-up, whether considering death from all causes or death with histopathologically confirmed melanoma metastasis.[13]

References

1. Singh AD, Bergman L, Seregard S: Uveal melanoma: epidemiologic aspects. Ophthalmol Clin North Am 18 (1): 75-84, viii, 2005.  [PUBMED Abstract]
   
   
2. Weis E, Shah CP, Lajous M, et al.: The association between host susceptibility factors and uveal melanoma: a meta-analysis. Arch Ophthalmol 124 (1): 54-60, 2006.  [PUBMED Abstract]
   
   
3. Yap-Veloso MI, Simmons RB, Simmons RJ: Iris melanomas: diagnosis and management. Int Ophthalmol Clin 37 (4): 87-100, 1997 Fall.  [PUBMED Abstract]
   
   
4. Eye and ocular adnexa. In: Rosai J: Ackerman’s Surgical Pathology. 8th ed. St. Louis, Mo: Mosby, 1996, pp 2449-2508. 
   
   
5. Avery RB, Mehta MP, Auchter RM, et al.: Intraocular melanoma. In: DeVita VT Jr, Hellman S, Rosenberg SA, eds.: Cancer: Principles and Practice of Oncology. 7th ed. Philadelphia, Pa: Lippincott Williams & Wilkins, 2005, pp 1800-24. 
   
   
6. McLean IW: Prognostic features of uveal melanoma. Ophthalmol Clin North Am 8 (1): 143-53, 1995. 
   
   
7. Gragoudas ES, Egan KM, Seddon JM, et al.: Survival of patients with metastases from uveal melanoma. Ophthalmology 98 (3): 383-9; discussion 390, 1991.  [PUBMED Abstract]
   
   
8. Introduction to melanocytic tumors of the uvea. In: Shields JA, Shields CL: Intraocular Tumors: A Text and Atlas. Philadelphia, Pa: Saunders, 1992, pp 45-59. 
   
   
9. White VA, Chambers JD, Courtright PD, et al.: Correlation of cytogenetic abnormalities with the outcome of patients with uveal melanoma. Cancer 83 (2): 354-9, 1998.  [PUBMED Abstract]
   
   
10. Zimmerman LE, McLean IW, Foster WD: Statistical analysis of follow-up data concerning uveal melanomas, and the influence of enucleation. Ophthalmology 87 (6): 557-64, 1980.  [PUBMED Abstract]
    
    
11. De Potter P, Shields CL, Shields JA: New treatment modalities for uveal melanoma. Curr Opin Ophthalmol 7 (3): 27-32, 1996.  [PUBMED Abstract]
    
    
12. Diener-West M, Earle JD, Fine SL, et al.: The COMS randomized trial of iodine 125 brachytherapy for choroidal melanoma, III: initial mortality findings. COMS Report No. 18. Arch Ophthalmol 119 (7): 969-82, 2001.  [PUBMED Abstract]
    
    
13. Collaborative Ocular Melanoma Study Group.: The COMS randomized trial of iodine 125 brachytherapy for choroidal melanoma: V. Twelve-year mortality rates and prognostic factors: COMS report No. 28. Arch Ophthalmol 124 (12): 1684-93, 2006.  [PUBMED Abstract]
    
    

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