CHOROIDAL METASTASIS

Choroidal metastasis is probably the most common intraocular malignancy, but it often goes undiagnosed, depending on the overall condition of the patient. These tumors often have a characteristic clinical appearance, and can often be treated to optimize the visual function and quality of life of the cancer patient. Depending on the type of primary cancer, many of these patients will already have a diagnosis of primary cancer elsewhere, which can aid in reaching the correct diagnosis. The most common etiologies of choroidal metastasis are breast carcinoma in women and lung carcinoma in men.

Symptoms

Metamorphopsia, peripheral field changes, and decreased visual acuity may result from direct tumor involvement of the macula or exudative retinal detachment.

Clinical Features

These tumors may be solitary or multiple, unilateral or bilateral, and they usually appear creamy-yellow, often with pigment mottling over the surface. They have a tendency to produce subretinal fluid and can cause a significant exudative retinal detachment. Most tumors are located in the posterior pole with a plaque or domed shape.

Ancillary Testing

Ultrasonography is helpful in distinguishing a choroidal metastasis from a melanoma. Whereas melanomas have low, regular internal reflectivity on A-scan ultrasonography, choroidal metastases usually have medium to high, irregular internal reflectivity due to the irregular arrangement of nests and chords of tumor cells within the choroid. By magnetic resonance imaging, these tumors are usually less hyperintense on T1 weighting than melanomas. In the absence of a known primary cancer, fine-needle aspiration biopsy may be required to reach the correct diagnosis.

Pathology/Pathogenesis

Histopathologically, choroidal metastasis appears with chords and nests of cancer cells (usually carcinoma) infiltrating the choroid. Choroidal metastases have been reported from virtually every site in the body.

Treatment/Prognosis

Observation may be appropriate in asymptomatic patients. Most tumors will respond to systemic chemotherapy or external beam radiation.

Systemic Evaluation

In patients suspected of having choroidal metastasis but with no known primary cancer, a thorough systemic workup for cancer of unknown etiology should be coordinated with a medical oncologist.

Multifocal, creamy choroidal deposits from metastatic breast carcinoma. Breast carcinoma is the most common cause of choroidal metastasis in women.

Multilobular amelanotic choroidal tumor in a patient with no history of systemic malignancy.

Solitary, vascularized choroidal metastasis from alveolar cell sarcoma in a 14-year-old.

A-scan ultrasonogram of the lesion in the previous figure. Note that the tumor has irregular, medium to high internal reflectivity consistent with a metastatic lesion.

Fine-needle aspiration biopsy of the choroidal tumor depicted in the previous two figures, demonstrating adenocarcinoma with formation of glandular structures.

Solitary, choroidal metastasis from breast cancer. Note that the tumor is relatively flat and yet produced a large, inferior exudative retinal detachment.

CHOROIDAL NEVUS

Choroidal nevus is the most common neoplasm of the uveal tract. This benign tumor usually arises early in life. It may grow slightly during puberty, but the vast majority remain benign throughout life. However, a few of these lesions will undergo malignant degeneration into

a choroidal melanoma, and an important diagnostic challenge is to distinguish a large choroidal nevus from a small choroidal melanoma.

Symptoms

Patients often have no symptoms, but metamorphopsia and blurred vision can result from subretinal fluid extending into the macula.

Clinical Features

Choroidal nevi are typically pigmented but can occasionally be amelanotic. They are located at the level of the choroid and usually have feathery, indistinct borders. They are usually flat or minimally elevated. Longstanding lesions often have drusen over the surface, which is a negative predictor of future growth. Features associated with a higher risk of growth include greater tumor thickness, posterior tumor margin touching the optic disc, subretinal fluid, and orange pigmentation

on the tumor surface. Documentation of significant growth must be viewed as a probable sign of malignant degeneration.

Ancillary Testing

Ultrasonography can occasionally be helpful in distinguishing a choroidal nevus from a nonmelanocytic lesion. Choroidal nevi that are more than 1.5 mm thick usually demonstrate low internal reflectivity on A-scan ultrasonography. Fluorescein angiographic features are not diagnostic but can support the diagnosis. Pigmented nevi are usually hypofluorescent in the early frames, with patchy hyperfluorescence as the study progresses. Pinpoint hotspots often coincide with clinical evidence of subretinal fluid, and are a risk factor for growth.

Pathology/Pathogenesis

Choroidal nevi arise from melanocytes in the uveal tract and appear histopathologically as low-grade spindle cell melanocytic tumors that replace the normal choroidal architecture. The pathogenesis is unknown. A strong family history of melanocytic tumors is uncommonly elicited, and there is no known relationship to sunlight exposure.

Treatment/Prognosis

Treatment is not usually necessary unless subretinal fluid affects vision, in which case treatment options include scatter laser photocoagulation, transpupillary thermotherapy, and plaque radiotherapy. If substantial growth is documented, the lesion is treated as a choroidal melanoma.

Systemic Evaluation

Systemic screening for metastasis is not necessary for a choroidal nevus unless the lesion degenerates into a melanoma. Examination of the skin for cutaneous nevi may rarely reveal evidence of multiple melanocytic lesions.

Fundus photograph of a typical choroidal nevus demonstrating a flat, pigmented lesion with feathery, indistinct borders.

This choroidal nevus is slightly elevated with feathery margins. Greater tumor thickness is associated with an increased risk of growth.

Relatively flat, pigmented choroidal nevus with drusen and fibrous metaplasia over the surface, indicative of chronicity.

Fundus photograph of a large, suspicious choroidal nevus with risk factors for growth such as orange lipofuscin pigmentation, a thin layer of subretinal fluid over the tumor surface, and posterior tumor margin touching the optic disc.

Fluorescein angiogram of a choroidal nevus, demonstrating late diffuse staining, leakage, and pinpoint hotspots, which are a risk factor for growth.

B-scan ultrasonography of a choroidal nevus. Note that the lesion is relatively thin.