CLINICAL

  POSTERIOR

FACED WITH A FRECKLE

IS THIS PATIENT’S CHOROIDAL LESION A MELANOMA OR A NEVUS?

SHERROL A. REYNOLDS, O.D., F.A.A.O.

A 57-YEAR-OLD white female presented complaining of blurry near vision. Her medical history revealed a diagnosis of a freckle OD five years prior and hypothyroidism, for which she was taking levothyroxine. The lesion measured about 4 disc diameters, had numerous overlying drusen, irregular margins and appeared flat. The patient did not have a history of ocular surgery, trauma or cancer, so choroidal metastasis was ruled out.

Was this patient’s freckle a choroidal melanoma or nevus?

Here, I discuss the etiology, symptoms, clinical signs and diagnosis/management of both entities to help you decide.

ETIOLOGY

Although choroidal melanomas are rare, they are the most common primary intraocular malignancy in adults. Specifically, they occur in about six in 1 million individuals, according to Cancer Control: Journal of the Moffitt Cancer Center. The risk factors for a choroidal melanoma are light-colored eyes (blue or gray), male gender, age 55 and older and Caucasian race (Black and Asian individuals are rarely affected). An increased risk is associated with chronic sunlight exposure, arc welding, tanning bed exposure and pigmentation like cutaneous freckles or iris nevi.

The 57-year-old’s hard-to-miss “freckle.”

Choroidal nevi are common benign lesions found in roughly 5% to 10% of the general population, according to Archives of Ophthalmology. Although they rarely evolve into malignant melanomas, they are a risk factor for them. Specifically, the annual transformation rate is about 1 in 8,845. By age 80, this risk is 0.78%, according to Ophthalmology.

SYMPTOMS

Patients with a choroidal melanoma can be asymptomatic or experience decreased vision, visual field defects, floaters or photopsias and pain, which can result from secondary glaucoma or tumor necrosis. Nevi have the potential to cause these symptoms if located near the fovea.

CLINICAL SIGNS

Choroidal melanomas and nevi can share several overlapping features, posing a diagnostic challenge. These features are color (pigmented, nonpigmented or amelanotic), size (you can have a large nevus or small melanoma), location, retinal pigment epithelial alterations (atrophy or hyperplasia) and more suspicious findings, such as serous retinal pigment detachment and a choroidal neovascular membrane. The good news is that choroidal melanoma and nevi have distinguishing features as well.

Choroidal melanoma:

• Indiscrete margins

• Irregular or oblong configuration: dome or collar-button shape

• Overlying subretinal fluid

• Lipofuscin (orange pigment)

• Vitreous hemorrhages or pigmented vitreous cells

• Proptosis

Choroidal nevi:

• Defined margins

• Flat or slightly elevated

• Halo (circular band of depigmentation surrounding pigmented nevus)

• Drusen

The smaller the melanoma at detection, the better the prognosis. An article in Archives of Ophthalmology included the proposal of the following mnemonic to distinguish a choroidal nevi from a melanoma, particularly small lesions: “To Find Small Ocular Melanoma Using Helpful Hints,” or “Thickness (greater than 2mm), Fluid (subretinal), Symptomatic, Orange pigment (lipofuscin), Margin near the optic nerve (within 3mm), Ultrasonography hollowness (vs. solid and flat) and Absence of Halo and drusen.”

DIAGNOSIS/MANAGEMENT

The following should be used to aid in the proper diagnosis:

• Retinal photography. This is necessary for documenting the lesion size, thickness characteristics and growth through time.

• Ultrasonography. A choroidal melanoma will demonstrate low to medium internal reflectivity, acoustic hollowness or a quiet zone at the base of the tumor and lesion thickness (>2mm). Other B-scan features suspicious for melanoma include excavation of choroidal tissue, sound attenuation, orbital shadowing and spontaneous vascular pulsations.

• SD-OCT. This helps to detect changes in the neurosensory retina and retinal pigmentary epithelium, such as serous retinal detachment, which can indicate a melanoma. A nevus will have photoreceptor loss, retinal atrophy and thinning and retinal pigment epithelial detachment.

• Enhanced depth imaging spectral-domain OCT. This provides enhanced visualization of the choroid, thus allowing for the assessment of tumor dimensions, thickness and cross-sectional detail. Characteristics of choroidal melanomas seen in EDI-OCT include intraretinal edema, loss of photoreceptor, inner segment outer segment (IS-OS) junction irregularity, choroidal shadowing and choriocapillaris thinning.

• Fundus autofluorescence. This will help to identify clumps of hyperautofluorescence that correlate with lipofuscin or “orange pigment,” which is observed with melanoma, and no autofluorescence, which is observed with nevi.

In terms of management, choroidal melanoma size dictates one’s course of action. According to the criteria of the “Collaborative Ocular Melanoma Study” (COMS), melanomas are classified using apical height and largest basal dimension in three groups: small (1 to 3.0 mm/5 to 16 mm), medium (2.5 to 10 mm/less than 16 mm), and large (>10mm/>16mm). Patients with medium to large and thicker melanomas have worse long-term prognoses, with a five-year mortality rate of 15% to 50% vs. individuals who have smaller melanomas, according to COMS. Several treatment options are available for choroidal melanomas, including plaque radiotherapy and enucleation.

Choroidal nevi should be managed based on risk of transforming into a choroidal melanoma. Using the TFSOM-UHHD mnemonic described above, patients with no risk factors should initially be managed with six-month follow-up, followed by yearly exams. Those who have one to two risk factors should be followed every four to six months for short and long-term lesion growth. Patients with three or more risk factors will show growth in more than 50% of cases, according to Archives of Ophthalmology. Therefore, refer them to ocular oncologists for further management and treatment.

Choroidal melanoma
Courtesy of Dr. Jay Haynie

THE ANSWER

If you diagnosed this patient with a choroidal nevus, you are correct! Retinal photos, ultrasound and SD-OCT, including EDI, were obtained and demonstrated lesion thickness < 2 mm. During the first year, she was monitored every six months, followed by annual exams, and the nevus has remained stable.

Choroidal melanomas are associated with dire consequences. However, early diagnosis and prompt referral can improve the patient’s outcome, including preserving his or her vision, so be vigilant in distinguishing between a choroidal melanoma and a nevus. OM

DR. REYNOLDS is an associate professor at the Nova Southeastern University College of Optometry and clinical preceptor/attending in the college’s diabetes and macular clinic. She is a fellow of the Optometric Retina Society and chairperson for the Florida Optometric Association Healthy Eyes Healthy People Committee. Comment at tinyurl.com/OMcomment.