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QUESTION
HOW DO I FOLLOW A PATIENT WITH A PRESUMED CHOROIDAL NEVUS?
Matthew A. Powers, MD, MBA
Prithvi Mruthyunjaya, MD, MHS
Choroidal melanocytic proliferations produce a range of clinical manifestations that include benign, premalignant, and malignant conditions. As the vast majority of these lesions are defined by their clinical features, and less commonly by a confirmatory biopsy, there can be some controversy and confusion over how to characterize and follow a particular lesion.
In our ocular oncology clinic, lesions are divided into 3 broad categories: (1) benign (low suspicion for malignancy), (2) indeterminate (medium to high suspicion for malignancy), and (3) malignant. To determine which category a lesion belongs in, we combine patient history with clinical examination, ancillary imaging studies, and standardized ultrasonography. The clinical challenge is to define reliable parameters for a particular benign or premalignant lesion that make it more or less likely to progress into a malignancy.
A benign choroidal nevus (BCN) is a common finding in the adult White population, although only 1/9000 will progress into malignant uveal melanoma (UM). BCN are typically minimally elevated, brown in color (but may be variably pigmented), and have a base between 1 and 10 mm and an apical height of less than 1.5 mm.1 In addition, BCN are characterized by a smooth surface and sometimes possess overlying drusen and retinal pigment epithelium (RPE) disruption, features which are often indications of chronicity (Figure 20-1). BCN can still exhibit normal growth at a slow rate, which should not be confused with malignant transformation. Less common but still benign conditions include choroidal melanocytosis, which is caused by hyperplasia of melanocytes and characterized by patchy areas of flat choroidal pigmentation, and choroidal freckle, which is caused by increased melanin without hyperplasia and presents as a flat pigmented lesion less than 2 disc diameters that remains stationary over time.
Figure 20-1. Choroidal nevus with overlying drusen, estimated to have a low risk for growth or malignant transformation.
Figure 20-2. ICL with moderate risk of growth and progression into a UM. Specifically, this demonstrates pigmented nevus with a more posterior location and subretinal fluid.
The more concerning lesion is what we refer to as an indeterminate choroidal lesion (ICL), sometimes called atypical or suspicious choroidal nevus. These are not definitively UM, but may exhibit one or more clinical features that historically are associated with an active UM. The presence of these features may represent risk factors for future growth and progression to malignant UM.
We specifically ask patients if they are having any visual symptoms that may suggest fluid exudation or lesion growth (eg, photopsias, visual field changes) and if they are, then we aggressively seek out any prior fundus photos to compare previous documentation of the lesion, including evidence of change or growth of the lesion.
Key clinical examination features to note include pigmentation pattern (predominantly melanotic, amelanotic, or mixed pigmentation), an estimate of the size and distance to the fovea and optic nerve (in millimeters or disc diameters), the presence of subretinal fluid (SRF) (eg, overlying or adjacent to the lesion), lipofuscin accumulation, characterized by orange pigment, presence of drusen, or associated RPE alterations near the lesion, indicative of previous SRF (also referred to as high water mark) (Figure 20-2). All lesions are photographed and optical coherence tomography (OCT) images of the lesion are obtained. A standard 10 MHz B-scan ultrasound probe is used to measure the lesion’s base and height. This baseline information is vital in formulating an accurate diagnosis and planning for future follow-up.
Figure 20-3. Widefield scanning laser ophthalmoscopy image clearly demonstrates the anatomical context of a large, posterior, pigmented lesion.
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