Choroidal Melanoma
March 3, 2020
San Diego County Optometric Society Newsletter: Retina Corner
By Nikolas J.S. London, MD FACS
President and Director of Clinical Research, Retina Consultants San Diego
Chief of Ophthalmology, Scripps Memorial Hospital La Jolla
Dear SDCOS membership,
Happy March, everyone. The holidays are behind us and spring is close at hand! Honestly, this is one of my favorite times of the year with a bit of lull in excitement and lots of time to spend with family. We just spent an amazing week in Steamboat Springs, Colorado – snowboarding with my 9 year-old through fresh powder, dog sledding through a state park, snowtubing on a ranch, and snowmobiling in the middle of a blizzard. It was incredible. Well, back to reality. Back in my fellowship, I had the privilege of training with Carol and Jerry Shields – the king and queen of ocular oncology, and two of the best mentors of my career. This month I thought it would be helpful to share some of the pearls they taught me about choroidal melanoma.
To start we should note that, while the most common primary intraocular malignancy, choroidal melanomas are rare, accounting for only 3.5% of all melanomas with an incidence of 6 patients per million. Choroidal melanomas arise of melanocytes of the uveal tract. Most patients are asymptomatic, with lesions discovered on routine exam as elevated, pigmented lesions deep to the retina. Patients are typically in their 50s to 80s, most commonly Caucasian. The key initial management point for choroidal melanoma is to distinguish it from much more common pigmented fundus lesions. The main differential diagnosis includes benign choroidal nevus, congenital hypertrophy of the RPE, metastatic lesions, hamartoma of the retina and RPE, hemorrhagic detachment of the retina, RPE, or choroid, and diffuse melanocytic proliferation.
Of these, the most important differentiation is between a choroidal nevus and a small choroidal melanoma. Differentiating small choroidal melanoma from choroidal nevus can be remembered using the mnemonic “to find small ocular melanoma” (TFSOM), where T = thickness greater than 2 mm, F = subretinal fluid, S = symptoms, O = orange pigment and M = margin touching optic disc. The rule of thumb is that melanocytic choroidal lesions that display two or more factors probably represent small choroidal melanomas, showing growth in over 50% of cases.
Fortunately, we have our examination and imaging modalities to look for these risk factors. Particularly helpful are ultrasonography, fundus autofluorescence, and OCT. Ultrasound is probably the key diagnostic test and when imaging choroidal melanoma, reveals low to medium internal reflectivity, as well as the dimensions of the lesion. Small choroidal melanoma is often characterized by orange pigment overlying the lesion. This fluid is rich and lipofuscin, and correlates with hyperautofluorescence on fundus autofluorescence imaging. Optical coherence tomography confirms the choroidal location and helps to confirm or exclude associated subretinal fluid.
Exam and imaging modalities will differ for other lesions on the differential diagnosis. Choroidal hemangioma is a circumscribed, round or oval lesion with variable coloration but not brown. The lesion is elevated, dome-shaped, and a solid mass on ultrasound with high internal reflectivity due to the presence of multiple vascular channels. Choroidal metastases are typically echo-dense on ultrasound with higher reflectivity than choroidal melanoma. OCT of choroidal metastases may reveal a lumpy bumpy configuration of the inner choroid. Lastly, CHRPE is a flat, pigmented lesion at the RPE. CHRPE is hypoautoflouorescence and OCT discloses flat, thickened, irregular RPE and absent RPE within lacunae.
I hope that this article was useful. As always, I welcome email or text curbside consultations of patients you are worried about, including cases you think might be choroidal melanoma.
Thanks again for reading. Please don’t ever hesitate to contact me.
Best wishes, and until next time,
