CHOROIDAL MELANOMA
Malignant Choroidal Melanoma
|
SIGNS AND SYMPTOMS
The benign choroidal melanoma, referred to clinically as a choroidal nevus, appears as a
flat or slightly elevated slate gray lesion of the posterior fundus. The margins are
typically indistinct, and often there are overlying areas of drusen noted within the
nevus. In most instances, choroidal nevi remain under two disc diameters (DD) in size,
although they may attain sizes of up to 5 DD in some cases.
The malignant choroidal melanoma, in contrast, appears as a mottled,
often significantly elevated lesion, ranging in coloration from white to greenish-gray. As
it grows, it may break through Bruch's membrane, taking on a mushroom-like appearance.
Serous retinal detachments are commonly associated with this presentation. You may also
observe overlying orange pigmentation known as lipofuscin. Most malignant melanomas are
over 10 DD in size at the time of diagnosis. Most patients with choroidal melanomas are
asymptomatic. However, should a significantly large lesion occur in proximity to the
macula, the patient may present with metamorphopsia, acuity loss, visual field deficit
and/or a hyperopic refractive shift.
PATHOPHYSIOLOGY
A choroidal melanoma represents a focal accumulation of melanocytes at the level of the
uvea. In a choroidal nevus, these melanocytes are normal in both form and function. In
malignant melanoma, the cells undergo neoplasia, reproducing at a faster rate than usual
and resulting in a dysfunctional tumor mass. This tumor is capable of not only local
extension but also of distant metastasis. While choroidal nevi do not typically lead to
this type of damage, it is believed that they can convert to malignancy; the rate of
malignant transformation over a 10-year period is estimated at 21 in 100,000.
Choroidal Nevus
|
MANAGEMENT
Nevi of 2 DD or less are harmless. Document the presentation with photography and, when
possible, perform a B-scan and follow-up annually. Nevi between 2 and 5 DD are more
suspicious. Either perform or refer for angiography to help differentiate the mass, and
follow-up regularly at six-month intervals.
When the lesion is greater than 5 DD, consider it a malignant melanoma
until proven otherwise. It may not require immediate treatment if relatively small and
demonstrates no growth. But if the presentation suddenly changes dramatically or if sight
is threatened, refer to a retinal specialist for treatment.
CLINICAL PEARLS
While a nevus is of little concern, malignant melanoma
presents a potentially life-threatening situation because of its propensity toward
metastasis. These tumors have been known to spread to the liver, lungs, skin and
gastrointestinal tract.
Refer patients with newly detected malignant melanomas to
a primary care physician for testing, which may include liver enzymes, carcinoembryonic
antigen (CEA), neuroimaging, and chest CT.
Other reports in this section
|
