Specimen of the Week 380: Malignant melanoma of the eye
By Subhadra Das, on 10 May 2019
Today’s specimen of the week comes from UCL Pathology Collections. The Collections are displayed at the UCL Pathology Museum at the Royal Free Campus of the UCL Medical School in Hampstead. The museum includes a medical teaching collection of nearly 3,000 specimens of human remains illustrating the history of disease. To open up these specialist medical displays to a wider audience, we’ve developed a trail of 10 specimens of well known diseases. As the museum only opens to the public for special events, we’re sharing the trail as part of the Specimen of the Week series.
In honour of Skin Cancer Awareness Month this May, today’s specimen of the week is a malignant melanoma of the eye.
Melanoma is a cancer — an uncontrolled growth of cells — that usually develops in the pigment-containing cells of the skin. The main cause of melanoma is over-exposure to ultra-violet light rays, either directly from sunlight or artificial sources like tanning beds.
Melanoma most commonly occurs in people with lighter skin, particularly white people living in tropical or subtropical climates. The highest instances of melanoma are in Australia and New Zealand.
If detected early, a melanoma can be surgically removed before it spreads to other parts of the body. Sadly, that wasn’t the case here.
This specimen is a rare, advanced example of melanoma developing in the eye. Melanoma usually occurs on the surface of the skin and so is relatively easy to diagnose. But this kind of cell growth can also occur in other organs of the body which contain pigment-producing cells, like the intestines and the eye. Because of the rarity of this kind of tumour in the eye, this melanoma went undetected in this patient until their death, caused by its spread to their liver.
Melanoma and other cancers are classified by pathologists as ‘neo-plastic diseases’, that is new, uncontrolled growth of cells. Like other cancers you have likely heard of — carcinoma, sarcoma, blastoma, lymphoma — the names for these growths combines the suffix ‘oma’ (meaning a mass of cells) with the Greek or Latin word describing the organ they from where they originated. In the case of melanoma, the source cells are the melanocytes which produce melanin, the natural pigment which gives colour to our eyes, skin and hair.
A melanoma growing in a person’s eye, like this one, grows in the uvea, consisting of the iris, ciliary body and the choroid which combined give colour to our eyes. Although rarer than melanomas of the skin, a melanoma in the eye, or uveal melanoma is considerably more deadly if it is able to spread to other parts of the body. When this happens, only 15% of people survive past 5 years. Unlike most cancers, which spread through the body’s lymphatic system, melanomas in the eye are usually spread through the bloodstream.
This week’s specimen is a reminder that much of medical diagnosis relies on finding things where they are expected to be found, and that the results can be deadly when the reality does not match our expectations. It’s important to point out, during Skin Cancer Awareness Month, that instances of skin cancer in people of colour tend to be underdiagnosed. This is in part because people with darker skin tend to develop melanomas in parts of the body not usually exposed to sunlight. Worse still, their rates of survival having been treated are significantly lower than white people treated for the same conditions.