What is ocular melanoma?
Ocular melanoma is a cancer of the eye. Melanoma usually develops in melanin rich sites like skin. Melanin is a pigmenting agent responsible for skin coloration. In the eye, melanin producing cells are present to provide specific colors to the eye. These ocular melanin producing cells if get an abnormal cell proliferation due to malignancy development cause ocular melanoma. Ocular melanoma is not same as skin melanoma.
Melanin is present in the innermost layer of the eye, therefore it cannot provide any alteration which is visible from outside. In addition, ocular melanoma is difficult to detect in early stage, as it is asymptomatic at that stage, therefore Ocular melanoma is called as silent killer.
The onset of ocular melanoma usually occurs at the adult age, but the aggressive nature of the this cancer often cause fatal for the affected individual. The ocular melanoma commences from the eye, but it can extend to the liver and often provide complexity.
In the maximum cases, ocular melanoma builds up gradually from the melanin producing cells present in the choroid (choroidal melanoma), besides this, it can extend from the melanin producing cells of the iris and ciliary body and termed as uveal melanoma. The iris and ciliary body are the part of the uvea.
In addition, uveal melanoma is described as
Iris melanoma: The iris is responsible for widening and narrowing of the eye, so the light rays can accordingly enter. Iris has melanin producing cells and therefore, it is a colored part of the eye. If uveal melanoma present in the iris, then it initially affects iris.
Melanoma in ciliary body – ciliary body is a muscular structure of the, which holds the lense and during setting the focal point, ciliary body assist in shaping the lens. If uveal melanoma is initially started from the ciliary body, then it termed as melanoma in the ciliary body.
Choroidal melanoma: – Choroid a coating of tissue that is present in the backside of the eye. It helps to create a reflection, as it situated behind the retina and assists to produce a picture. If uveal melanoma is initially started from the Choroid, then it termed as Choroidal melanomas and the most frequently found the ocular melanoma. (1,2)
In most of the ocular melanoma is asymptomatic in an initial stage. But the following sign and symptoms may gradually arise depending upon the site of the cancer development.
- An emergent murky spot on the iris
- An impression of blinking lights
- An alteration in the pupil ( the dark circular shape present at the center of the eye)
- Eye power is decreased on the affected eye, therefore blurred vision or poor sight in one eye
- Tangential vision loss
- Sensation of floaters or flecks of dust interferes the vision. (1)
The exact cause of the ocular melanoma is not identified, but from different study outcomes it is identified that there is a close linkage between sun exposure and that an OM tumor development.
The similarity observed between cutaneous melanoma and ocular melanoma is in the both the condition is associated with lack of KIT, BRAF and NRAS mutations. Other than these, a genetic profiling discovered in ocular melanoma is an abnormal genetic mutation in the GNA11 and GNAQ genes.
Almost 75% of the affected individuals identified with abnormal genetic mutation in the GNAQ and GNA11genes. Another common genetic abnormal mutation is associated with BAP1 gene. Ocular melanoma has unique genetic modification and a robust propensity to metastases to the liver.(2,3)
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Staging of the Ocular melanoma is very important for developing the treatment plan. The detailed staging is conducted by analyzing the TNM system.
The TNM based staging assisting to provide following information:
- Analyzing of T provides the information of the primary tumor shape, size and also invading nature towards subsequent structures.
- Analyzing of N helps to provide information like spreading of Tumor to subsequent lymph nodes .
- Analyzing of M helps to provide information that cancer spreads in the distant part of the body.
The TNM analyzing need very detailed process, but in clinical practice, several oncologists use the straightforward staging system depends upon the size of the tumor after checking it’s malignancy nature. This system segregates ocular melanomas into small, medium, and large:
- Small: involving 1 mm and 3 mm in elevation and transversely it varies in between 5 mm and 16 mm
- Medium: involving 1 mm and 8 mm in elevation and transversely tumor does not exceed 16 mm
- Large: elevation is more than 8 mm or transversely tumor exceeds 16 mm. (4)
Depending upon the stage of the ocular melanoma, treatment plan is made. The following are the treatment options associated with ocular melanoma:
Surgical removal of the melanoma (tumor) and associated healthy tissues surrounded the tumor due to stopping the spreading of carcinoma.
The complete removal of the entire ocular structure.
Over a period of time, dynamic powered radiation rays, including protons or gamma rays are given to the tumor present in the eye to kill melanoma cells. The radiation therapy is generally recommended for medium to small sized eye melanomas.
In some cases, laser rays are given to kill the melanoma cells present in the eye tumor. Infrared laser therapy along with radiation also recommended for some treatment plan.
Excrete lower temperature freezing technique may also apply to melanoma cell necrosis, but this technique is not readily used to treat Ocular melanoma. (1,5)
If melanoma is restricted in the eye only, then approximately 80% of affected individuals can survive 5 years, whereas if ocular melanoma has spread to distant parts, like liver then only 15% affected individuals have a 5-year relative survival rate. (6)
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In most of the cases, it has been identified that Ocular melanoma is associated with atypical mole syndrome, which is also known as dysplastic naevus syndrome. Dysplastic naevus syndrome and skin melanoma have also a great clinical amalgamation. More than 100 moles with some atypical shape and size present on their body.
The ocular melanoma has a higher incidence rate and almost 2,500 adults are screened in every year. It has been also observed that the faired skin people with blue eyes are mostly affected by the ocular melanoma, but the cause behind this is not yet identified.
Half of the OM affected people get affected with metastases within 10 to 15 years after diagnosis, though in some cases, metastases is detected even after 20-25 years after their initial diagnosis and it has been well known that metastatic condition becomes fatal for the affected individual.
The mortality rate associated with half of the patients with OM is unbothered even with the treatment advancement of therapeutic management of the primary eye tumor. In future, more clinical and medical research required to control the patient outcomes.(2)
- Mayo Clinic Staff, (2015); Eye melanoma; Retrieve from: http://www.mayoclinic.org/diseases-conditions/eye-melanoma/basics/symptoms/con-20027875
- About Ocular Melanoma; Ocular Melanoma Foundation; Retrieve from: http://www.ocularmelanoma.org/disease.htm
- Ocular Melanoma; Melanoma Research Foundation; Retrieve from: https://www.melanoma.org/understand-melanoma/what-is-melanoma/ocular-melanoma
- Eye Cancer (Melanoma and Lymphoma); American Cancer Society; Retrieve from: http://www.cancer.org/cancer/eyecancer/detailedguide/eye-cancer-staging
- Ocular Melanoma Treatment Options; Melanoma Research Foundation; Retrieve from: https://www.melanoma.org/understand-melanoma/what-is-melanoma/ocular-melanoma/ocular-melanoma-treatment
- Eye cancer survival rates; American Cancer Society; Retrieve from: http://www.cancer.org/cancer/eyecancer/detailedguide/eye-cancer-survival-rates
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