Most Common Primary Malignant Intraocular Tumor Biology Essay

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Choroidal melanoma is the most common primary malignant intraocular tumor in an adult. Usually arises from the melanocytes within the choroid. Most of the time, the tumor comes from preexisting melanocytic nevi. The growth of the tumor can occur silently, but symptoms of blurred vision, paracentral sctoma, painless and progressive field loss, floaters and severe ocular pain has been reported. There are many factors that could of lead to the malignant tumor one of which is sunlight exposure others are family history, history of nevus, congenital ocular melanocytosis, dysplastic nevus syndrome, xeroderma pigmentosum. Treatment to this form of melanoma is dependent on size of the cancer, but brachytherapy and enucleation are the two most common type. Prognosis is also dependent on size of the tumor which can vary from 14.9% to 61% mortality rate within 10 years. This case report will show how to diagnose and manage patients who you suspect of having chorodial melanoma.

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Introduction

Choroidal Melanoma is a rare malignant intraocular tumor. Choroidal Melanoma is a subtype of uveal melanoma. Anterior uveal melanomas are tumors that come from the iris and posterior melanoma comes from the choroid or ciliary body.

Signs and symptoms

Choroidal melanoma starts out as nodular or dome-shaped and is well-circumscribed and become irregular configurations such as multilobular or mushroom shape as it grows. Some unusual tumor has a diffuse growth patterns and grows lateral with very little elevation. This makes it hard to detect and once diagnose it can often lead to exudative retinal detachment. The melanoma can have very different color, from amelanotic to dark pigmented. The lighter the tumor the easier it is to see the vasculature. There are also sometimes dursen present along with spots of atrophy and some parts with orange discoloration. The orange discoloration is highly suggestive of malignancy. If there is a large exudative retinal detachment, subretinal hemorrhage or a vitreous hemorrhage it could obscure the view therefore it will make the detection of the melanoma more difficult. If the choroidal melanoma is further anterior, signs of sentinel vessesls, which are dilated episclearal vessels that can be seen thought the conjunctiva, will be present because the tumor requires a large blood supply for its high metabolic demands. According to the collaborative Ocular Melanoma Study (COMS), choroidal melanoma are accurately diagnose to 99.52%. When choroidal melanoma diagnosis has been made, a complete physical should also be performed to find any site of metastasis, particularly in the liver and on the skin.

Choroidal melanomas can stay asymptomatic for an extended period of time and can only be detected through ophthalmoscopy. The symptoms can be delay the more anterior the lesion originated from. As the melanoma grows symptoms such as blurry vision can occur due to growth onto the fovea. Other causes of the blurred vision could be cystoid macular edema, retinal detachment, and vitreous hemorrhage. If the growth of the melanoma becomes large enough it could block the visual axis which can cause a progressive visual field loss. Floaters could be due to necrosis of areas in and around the tumor causing vitreous hemorrhage or hyphema. Ocular pain can occur if the choroidal melanoma presses on the posterior ciliary nerves or high intraocular pressure from acute angle-closure glaucoma.

Etiology

Choroidal melanoma usually occurs in people with lighter pigmented irides. This is one of the main factors that lead to researchers to believe sunlight is the main cause of the tumor. Another cause is the genetic factor; people with family history of uveal melanoma will have a higher chance of having the same condition. Unlike cutaneous melanoma, which has link to mutation of the BRAF, ocular melanoma does not have similar mutation; instead it has mutations in GNAQ and GNA11 gene. Other preexisting conditions such as uveal nevus, xeroderma pigmentosum, congenital ocular melanocytosis and dysplastic nevus syndrome can lead to choroidal melanoma.

Epidemiology

Occurrence of choroidal melanoma is about 6 cases per 1 million per year. Even though this is rare, it is still the most common primary intraocular tumor and second most primary malignant melanoma in the whole body. Incidence peak around 55 years of age and more often affect white of northern European descent. Choroidal melanoma in children and blacks are extremely rare, and occurrence in Hispanic and Asians are somewhere in between black and white. There is more a prevalence in male except for the age of 20-39.

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Associated factors

Case Report

A 31-year-old white male presented to our clinic on August 9, 2012, complaining of blurry vision in the distance. The changes in his vision were mild, gradual onset and in both eyes with no other associated factors. His last eye exam was in 2006, in which he got a new spectacle prescription, and he reports a normal outcome from the exam and denies any pathology. The patient does occasionally wear his glasses for distances corrections, but noted that lenses are scratched and becoming difficult to see through them. Patient's medical and ocular history was unremarkable along with his family medial and ocular history. The patient does not have any know allergies, but is taking Claritin D for seasonal allergies and multivitamins as a preventative measure. He drinks alcohol socially and denies any tobacco product. The patient was in a good mood and was oriented to time, place and person.

Patient's entering visual acuity with his 6-year-old glasses were 20/25+ OD 20/20 OS and 20/20 OU at distance and 20/20 OD, OS, OU at near. Best-corrected visual acuity was 20/20 OD, OS, OU at distance and near with a manifest refraction of -0.50 -1.00 x 159 OD and -0.50 -0.50 x 059 OS. Pupils were equal round and reactive to light, with no afferent pupil defect. Confrontation fields were full to finger count OD and OS. Extraocular muscles were smooth full range of motions in both eyes with no pain, and no diplopia reported. Cover test reveals orthophoria at distance and 3 ^ exophoria at near. Upon slit lamp examination, lids and lashes were normal OU, conjunctiva was white and clear, and cornea was also clear and intact. In the iris, the right eye was blue and flat and in the left eye there was a brown nevus located from 4 o'clock to 10 o'clock.

There was an even tear film with a tear break up time of 12 seconds/ OU. Anterior Chambers was deep and quiet without cells or flare and angles were 4/4 OU through VonHerrick. Pressures were done through Goldman 10mmHg OD, OS. We then proceed to dilate the patient with 1 drop of paremyd and 1 drop of Tropicamide OD, OS. Upon dilated fundus examination, with a Digital Wide Field and a Binocular Indirect Opthalmoloscope, the lens was clear and normal in both eyes. The optic nerves were normal with a cup-to disc ratio of .15H/.15V OU. The neuroretinal rims were healthy and intact. Vessels were normal and the arterial-venous ratio was 2/3 in both eyes. The macula was flat and normal OU. The peripheral temporal right eye however shown a raised elevated lesion >2mm well demarcated. The lesion looks dome-shaped and the color is grey-green with orange shaped patches with presence of subretinal fluid. The melanoma is about 15mm in length with no signs of exudative retinal detachment, subretinal hemorrhage and no sign of vitreous hemorrhage, which are signs of choroidal melanoma. The left eye peripheral retina was flat an intact with no signs of pathology.

The differential diagnoses for this case include:

Choroidal Nevus

Congenital hypertrophy of the RPE

Reactive hyperplasia of the RPE

Choroidal Detachment

Choroidal Nevus is flat or with only minimal elevation of a pigment or nonpigmented lesion.

Congenital hypertrophy of the RPE present with flat black lesion and crisp margins in the peripheral fundus. Usually surrounded by depigmented or pigmented halo.

Reactive hyperplasia of the RPE has a history of previous trauma or inflammation. Presentation is a black, flat and irregular margins and often mutifocal.

Choroidal Detachment is usually follows ocular surgery, trauma, or hypotony. Presentation is dark peripheral multilobular, smooth, bullous, orange-brown elevation of retina and choroid. Usually extends 360 degrees in the periphery and in a lobular configuration. The ora serrata is visible without scleral depression. IVFA is the study of choice to help differentiate between the two.

The patient did not have a history of trauma, surgery, or infections to the eye, so it ruled out reactive hyperplasia and choroidal detachment. The presentation of the lesion looks like it was elevated greater than 2mm and it has a grey-green coloration, which could rule out choroidal nevus and congenital hypertrophy. So from history and presentation, the pigmented lesion is highly suspicious of choroidal melanoma. Further testing need to be done, but due to lack of equipment the patient is refer to ophthalmology to confirm choroidal melanoma.

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Ophthalmology Report

Ophthalmology confirms our suspicion that it was a choroidal melanoma. Through IVFA and B-Scan they determine that it was a medium size tumor and they would refer to ocular oncology. The IVFA rule out lesions that may look like a melanoma, but it cannot differentiate between a melanoma from a large nevus, metastases or hemangioma. The B-scan was used to document the thickness and to confirm clinical findings. The options the patient was given is to remove the eye or go through radiation therapy.

Discussion

Choroidal melanoma arises from uncontrolled growth of melanocytes. Three distinct cell type, spindle A, spindle B, and epitheloid have been identified as in choroidal melanoma. Epitheloid is the most aggressive type and has the poorest prognosis of the three. As they grow the tumor can break through the Bruch membrane, which leads to a mushroom shape appearance. Bilobar, mutilobular and diffuse appearance can also be seen. The diffuse appearance has more of a lateral growth with minimal elevations. Rarely does the origin comes from multiple spot, usually has a center area where the growth begin. The retinal pigment epithelium can be affected when the melanoma pushes against it causing poor circulation. The retinal pigment epithelium will develop areas of atrophy, drusen, and localized pigment epithelial detachments. (medscape) The changes in color are cellular debris from the melanocytes that are digested, which gives it an orange color. Changes can lead to neovascularization over the tumor which leads to subretinal exudates, hemorrhage and plaque formation. As the tumor grew, loss of vision can occur because of the ischemia causing the degeneration of the retinal photoreceptors and retinal neurons. Cystoid macular edema is also a sign because of the tumor can cause a separation of the cystoid spaces and larger schisis cavities.

The patient normally does not notice any symptoms and the further it is away from the optic nerve and the fovea the larger the melanoma can grow undetected. The exudative fluids underneath the subretinal space would lead to a retinal detachment, which would cause a more significant field loss. Even though rare, there could be serve pain if the tumor presses on the posterior ciliary nerves. If there is growth anteriorly then the ciliary body, trabecular meshwork and lens will all be affected. This could lead to ocular hypotension or hypertension and cataracts can form as a result. Metastasizes tends to occur even before a diagnosis is made. The cause of death is secondary to distant metastases most likely to the liver. The lung, bone, skin and central nervous system can also be affected.

A-scan ultrasonography is useful to detect elevations when it is greater than 2-3mm thick. The scan shows a prominent spike and followed by low-to-medium internal reflectivity with diminishing amplitude and significant echo. (medscape) The A-scan ultrasound can be as accurate as 95% in the diagnosis and it can also measure the dimension. Preforming A-scans over a period of time can help determine a diagnosis when it is too hard to tell.

B-scan is normally used to determine if there is a mass present and it is also useful when there is a block making hard to make a diagnosis. Not only does B-scan help to establish a diagnosis, it is also useful to monitor the tumor size and if there is any extraocular involvement. There are quite a few distinct features that can be seen in an ultrasound. Some of these signs are low-to-medium reflectivity, excavation of underlying uveal tissue, shadowing of subjacent soft tissues, internal vascularity and an acoustic quiet zone at the base of the tumor called acoustic hollowing. (Medscape). Ultrasound biomicroscopy is useful when the choroidal melanoma affects the anterior segment.

Fluorescein angiography and indocyanine green can help point to a diagnosis but it does not have a pathognomonic signs. Small choroidal melanoma can show hypofluorescence because of the blockage of the background, or it shows a normal angiography. Large melanoma has an early hypofluorescence and hyperfluorescence, which then has a late intense staining. Angiography can also show intrinsic vascularization and signs called the double circulation patterns are seen. Double circulation pattern shows simultaneous fluorescence of retinal and choroidal circulation within the tumor (Medscape).

Computed tomography can also be used but it is not as sensitive as ultrasonography and it is more expensive. It is useful if there is any extraocular extension, but it is unable to distinguish between choroidal or retinal detachment and a solid tumor. When preforming CT with contrast however choroidal melanoma shows enhancement. Also CT is sensitive in detecting calcium which is more commonly found in choroidal osteoma rather than choroidal melanoma. Although MRI is more expensive than CT scans and with contrast it provides a better resolution, it still is less sensitive than ultrasonography. MRI is useful in cases where there is suspicion of extrascleral extension of the tumor or to differentiate the fluid around the melanoma.

Biopsy is usually not required, but it can help in differentiating between an amelanotic melanomas from metastatic tumors. When ancillary test are unclear and in difficult diagnostic cases a biopsy is required. With tumor size greater than 3mm there is 95% accuracy. Although incisional biopsy is more invasive and can lead to more complications it has less of a false-negative and false-positive results. Histological evaluation can confirm the diagnosis and can determine the prognosis.

When deciding how to treat the melanoma factors such as visual acuity, size of the tumor, age and general health, ocular structures involved and if there is presence of metastases. Smaller tumor 2-2.5 mm in elevation and less than 10mm in diameter can be treated with observation. This is controversial because the idea of not treating a melanoma is unacceptable in the past. But according to the COMS, observations as a treatment is acceptable for small choroidal melanoma due to no significant survival rate with enucleation and observations can preserve the patient's sight. With medium size melanoma studies shows that there are no significant differences between radiation therapy and enucleation. For a large melanoma there is no difference between enucleation after radiation therapy and enucleation without radiation therapy. Even though there is micrometastasis at the time of diagnosis, if no systemic involvement is found then there is no indication for systemic chemotherapy. 

Enucleation is the preferred treatment for a large melanoma or when other treatment has failed. Enucleation is also recommended when it caused complications to the visual functions.