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Ophthalmology – Choroidal Melanoma
Choroidal melanoma is the most common primary intraocular malignancy, arising from melanocytes within the uveal tract. The majority of cases (about 90%) involve the choroid, with smaller proportions affecting the iris or ciliary body. These tumors may appear pigmented, nonpigmented, or mixed, and typically present as dome-shaped, mushroom-shaped, or diffuse lesions. They are often associated with subretinal fluid, orange pigment (lipofuscin), and occasionally hemorrhage. Any suspicious pigmented lesion in the fundus must be carefully evaluated for possible melanoma.
Epidemiologically, choroidal melanoma most commonly occurs in middle-aged adults, with a median age of around 55 years. It is more prevalent in fair-skinned, blue-eyed individuals, particularly those with a tendency to sunburn. The incidence in the United States is approximately 4–6 cases per million in Caucasians and lower in other populations. Although rare in children, it can occur in all age groups. Approximately 2,500 new cases are diagnosed annually in the United States.
Risk factors include light skin pigmentation, oculodermal melanocytosis (Nevus of Ota), and preexisting choroidal nevi with high-risk features such as increased thickness, subretinal fluid, symptoms, and the presence of orange pigment. Genetic studies have shown that chromosomal abnormalities, particularly monosomy 3 and duplication of chromosome 8q, are associated with a worse prognosis and increased risk of metastasis.
The pathophysiology involves malignant transformation of melanocytes within the choroid. These tumors may arise de novo or from preexisting benign lesions such as choroidal nevi. As the tumor grows, it can disrupt surrounding structures, leading to retinal detachment, photoreceptor damage, and vision loss.
Clinically, patients may present with decreased vision, flashes, floaters, or may remain asymptomatic in early stages. On examination, the tumor typically appears as a pigmented or amelanotic mass, most commonly located in the posterior segment. Associated findings may include subretinal fluid, retinal detachment, and lipofuscin deposits. The lesion’s size, location, and proximity to the optic disc or fovea are important in determining prognosis and management.
Diagnosis relies on clinical examination and multimodal imaging. Fundus photography, ultrasonography, fluorescein angiography, indocyanine green angiography, and optical coherence tomography are commonly used. Ultrasonography is particularly useful in identifying the internal acoustic characteristics of the tumor. In selected cases, fine needle aspiration biopsy may be performed to confirm diagnosis and evaluate cytogenetic markers. Systemic evaluation, including liver function tests and imaging such as liver MRI or PET scan, is essential to detect metastasis, as the liver is the most common site of spread.
Management depends on tumor size, location, and patient factors. Treatment options include plaque radiotherapy, proton beam therapy, surgical resection, transpupillary thermotherapy, and enucleation. Plaque radiotherapy and proton beam therapy are commonly used for small to medium-sized tumors and offer high rates of local tumor control. Enucleation is reserved for large tumors or those with complications such as glaucoma or extraocular extension.
Prognosis is closely related to tumor size and genetic features. The risk of metastasis increases with tumor thickness, ranging from approximately 12% for small tumors to 50% for large tumors at 10 years. Despite effective local control, metastatic disease significantly worsens survival. Visual outcomes depend on tumor location and treatment modality, with many patients experiencing vision loss after radiotherapy.
Complications vary depending on treatment. Enucleation may result in cosmetic and socket-related issues, while radiotherapy can lead to radiation retinopathy, optic neuropathy, cataract, glaucoma, and eventual loss of the eye. Lifelong follow-up is essential to monitor for recurrence and systemic metastasis.
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