Nov 2016

Choroidal melanoma: a spotter’s guide
BY PETER HADDEN*
There are not many truly life-threatening
ocular conditions, but choroidal melanoma
is certainly one of them. Overall, about 50%
of people diagnosed with it will, in the fullness
of time, die from it, so one can certainly say that
it is something no one wants to miss. Missing it
has been the subject of lawsuits in the USA and,
even in New Zealand, this diagnosis has graced
the adverse comments section of our Health and
Disability Commission, wondering if “x failed to
provide services with reasonable care and skill…”.
Luckily, that happened 16 years ago (before my
time, may I add!), but we certainly don’t want it to
come up again. So how can we avoid that?
Obviously the first step is not to miss the
diagnosis. Unfortunately, although melanoma is
rare, naevi are not and sometimes the differences
can be subtle. Furthermore, the only time when
maybe we might be able to make a difference to
the prognosis, ie. reduce the risk of metastatic
disease in the future, is if we can catch and treat
melanomas when they’re small, which of course is
when they are most easily confused for naevi.
One study found that, for small indeterminate
pigmented tumours, ie. ones that might be
naevi or might be melanoma, there was a 5%
cumulative chance of metastatic death for
each of the following risk factors: margin at the
disc, lipofuscin, symptoms and subretinal fluid.
Therefore if you’ve got all four there’s a 20%
chance you’ll be dead in a few years.
Some bright spark then came up with a
mnemonic to help people remember what to look
for if you think you’ve seen a naevus but don’t
want to miss a small melanoma (small being less
than 2.5mm thick). That mnemonic is “To find
small ocular melanoma”. This stands for thickness,
fluid, symptoms, orange pigment and margin at
the disc. Naturally of course others subsequently
pointed out that this didn’t really cover everything;
ophthalmologists routinely do an ultrasound
(B-scan) on all such lesions and therefore we
routinely add two letters to this, looking for
hypoechogenicity and characteristic shapes (as
well as the thickness, which ultrasound is very
good at measuring). Then of course, documented
growth is another risk factor. Fortunately many
of you probably don’t have ultrasound anyway so
you don’t have to remember those two letters, but
do remember to look at old photos to see if it has
changed.
It might be helpful at this juncture to go over
what each of these “suspicious features” actually
are:
T is for thickness
If it’s more than 2mm thick, that’s a bad sign. This
suspicious feature actually is best appreciated by
ultrasound, since on ultrasound you can measure it
very easily, as previously mentioned. But if you’ve
got OCT, you can switch on “enhanced depth
imaging” (EDI) or push the OCT machine forward
so that the image flips and you can get a pretty
image of the choroid and usually you can measure
the thickness of the tumour on this, but only if it’s
less than about 1mm thick.
F is for fluid
Subretinal fluid is a danger sign. Naevi can often
have a bit of fluid over the top of them, which
doesn’t matter, but if it’s leaking fluid around it,
that’s bad (unless of course it’s from something
else, like a choroidal neovascular membrane, which
you can get with naevi). Often you can see this
around the tumour or, if you get the patient to look
down, you might notice an inferior serous retinal
detachment. However, even a small bit of fluid is
important to spot and so if you’ve got a camera,
try putting it on autofluorescence; if it’s leaking
fluid, this will show up white beside the tumour.
OCT of course also comes in handy here, as it will
show fluid directly.
S is for symptoms
If your patient has an itchy eye, that’s a symptom
but it really doesn’t have anything to do with
whether there’s a naevus or melanoma in the
fluid. Pain doesn’t matter either (unless it’s huge,
melanoma is not associated with pain, and most
people would suspect that something’s amiss if
you have a really massive melanoma that takes up
the whole eye. The symptoms that really matter
are visual loss (not attributable to some other
cause, of course), field loss or flashes. The flashes
that you get with melanoma are different from the
Moore’s lightening streaks of vitreoretinal traction.
They tend to last longer, maybe a few minutes,
move slowly around, sometimes in circular
Pic 1&2. A small choroidal melanoma. Note the visible subretinal fluid and orange
pigment (lipofuscin). This patient was also symptomatic, with blurred vision and
flashing lights, as this tumour was under the fovea.
patterns, sometimes like a lava lamp, and aren’t
always temporal but instead can be anywhere. Ask
the patient if they’ve noticed any funny lights if
you’re wondering about melanoma.
O is for orange pigment
Orange pigment, ie. lipofuscin, is bad. Sometimes
it can be hard to see – it doesn’t stand out as
well as drusen against a dark background like a
melanoma, but is easier to see with an indirect
(where it kind of looks like someone’s got an
orange pepper shaker and shaken it across the
tumour). On autofluorescence, which you may
have on your camera, it shows up very obviously
as very light white spots over the tumour. One
caveat, however, RPE changes and drusen, both of
which are good signs (see below), can also show
up light on autofluorescence, but RPE changes
look more “geographic” (like how scattered islands
might look on a black and white map) and drusen
just don’t light up as much – no one said that
autofluorescence was completely straight forward!
M is for margin at the disc
This one’s easy. If the tumour is at the disc, or
within a disc diameter of the disc, then that’s a
suspicious feature.
Pic 3 (above). A colour photo and EDI OCT of a melanoma. Note the lipofuscin (orange pigment) on the tumour, the obvious tumour in the
choroid on EDI and the subretinal fluid above it which extends outside the borders of the tumour. Pic 4 (below). A colour photo and fundus
autofluorescence (FAF) image of a peripapillary melanoma. Note how the fluid shows up very brightly just below the melanoma. The central,
thickest part of the melanoma is dark, indicating RPE changes, but they aren’t very marked.
There are also a couple of signs that imply it’s
just a naevus. Drusen over the surface of it or RPE
changes such as hyper or hypopigmentation either
over the top of the tumour or around it, imply that
it’s been there a long time. That of course means
that it’s probably a naevus, as melanomas usually
haven’t been there a long time (or else they’d be
bigger). Melanomas are usually much more evenly
coloured and have a very distinct border without
RPE changes around them (for some reason,
some people seem to have the impression that an
indistinct border is bad; this is distinctly untrue).
There are also other pigmented things in the eye;
choroidal freckles, melanocytomas and CHRPEs
to name a few. Often also choroidal neovascular
membranes look pigmented too. Little spots
of pigment also are common in the retina. The
key thing with most of these is that they don’t
have the above features, except for pigmented
scleral crescents beside the optic disc, commonly
temporally – but these are flat and don’t have any
of the other features.
The bottom line has to be that, at the least, any
pigmented tumour with any of the suspicious
features mentioned has to be seen by an
ophthalmologist, except for little spots of pigment
that are otherwise completely benign looking
beside the disc. Those with suspicious
features will be offered treatment, but
it depends on how suspicious it is, how
worried the patient is and how badly
treatment of it will affect the vision as to
whether treatment will be delivered. If it
is watched, the standard recommendation
is to see it again in three months and then
once a year, to look for growth. This is often
done by optometrists and the main thing
here really is to make sure you look back
at the old photos to make sure it hasn’t
changed. Sometimes even with photos it
can be hard – if a photo is overexposed, it
might make the very thin pigmented border
of the tumour invisible and then, on a
subsequent normally-exposed photo, it will
look bigger. If you have autofluorescence,
make sure you do take an autofluorescence image
at the start because often the borders can be
much easier to see and less open to problems with
exposure than standard photos. Photos taken with
a red filter can also be useful, for the same reason;
they image pigmented choroidal tumours better
since they are less absorbed in the overlying retina
and RPE.
Good luck then with spotting naevi! And if you’re
thinking of buying a camera, consider one that
does autofluorescence; it’s useful in many other
conditions with fluid and RPE changes too, like
macular degeneration and dystrophies. ▀
ABOUT THE AUTHOR
* Dr Peter Hadden practises
at Eye Institute Remuera and
New Lynn, Retina Specialists
and Greenlane Clinical Centre
in Auckland, subspecialising
in vitreoretinal surgery and
adult chorioretinal tumours,
as well as performing
cataract surgery.
November 2016
NEW ZEALAND OPTICS
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