Check Up #21 - Can Melanoma occur outside the skin?

But it isn’t only a skin cancer: there exist other, though much rarer, forms of malignant melanoma that can develop in other parts of the body.

For instance, mucosal melanoma occurs on mucous membranes, which line various cavities in the body. Mucosal melanomas can be found in the head and neck, the anorectal region, the vulvovaginal region and the urinary tract. These melanomas have a poorer prognosis than skin melanomas.

And there are also uveal, or ocular, melanomas, a type of eye cancer that appears in the uvea, which lies under the sclera, the white membrane of the eye. The uvea comprises the iris, the colored part of the eye; the choroid, a dense network of blood vessels and pigmented connective tissue located between the retina and the sclera; and the cilliary body, the structure that produces the fluid in the eye. Although much rarer than cutaneous melanoma, there are several million new cases of uveal melanoma per year. When uveal melanoma spreads (50%), 90% of the time it spreads to the liver. Uveal melanomas are difficult to diagnose because they are often asymptomatic.

Oliver Sacks, the british-born neurologist famous for his wonderful “clinical tales” (such as “The man who mistook his wife for a hat”) and his books (such as “Awakenings” which was made into a movie starring Robert de Niro and Robin Williams), was diagnosed with ocular melanoma in 2006, and wrote about his experience in his book “The Mind's Eye”, published in 2010. 

Given the complexities of uveal melanoma, and although it doesn’t fall within the Champalimaud Foundation's primary focus – which is cutaneous and mucosal melanoma –, the institution collaborated as a partner in an international consortium called UM Cure 2020. This five-year initiative aimed to validate novel therapeutic approaches at the pre-clinical stage for metastatic uveal melanoma.

Melanomas begin in cells called melanocytes, which are cells found in the upper layer of the skin that produce a pigment known as melanin. Melanin gives skin its color and is responsible for tanning. In the eye, there are melanocytes in the pigmented parts of the uvea. There are also melanocytes in mucous tissue – in particular in the nasal cavity, the cochlea of the ear and the brain.

By far the most important risk factor for developing cutaneous melanoma – the incidence of which, as mentioned above, far outweighs any other form of melanoma – is exposure to UV radiation (from the sun or sunbeds), which causes an accumulation of potentially carcinogenic genetic mutations.

Cutaneous melanoma can be treated if detected early enough, but dermatologists agree that the best strategy is to avoid excessive exposure to UV radiation. According to the Portuguese League Against Cancer (Liga Portuguesa contra o Cancro), there are around 1,500 new cases of melanoma every year in Portugal.

We will come back more in depth to the topic of cutaneous melanoma in an interview with two doctors from the Foundation’s Dermatology Unit, which will be published on this site in a few week’s time.

Sources:

https://medlineplus.gov/
https://www.skincancer.org/
https://www.ligacontracancro.pt/
https://www.mayoclinic.org/
https://www.ncbi.nlm.nih.gov/
https://institut-curie.org/
https://fchampalimaud.org/
 

By Ana Gerschenfeld, Health & Science Writer of the Champalimaud Foundation.

Reviewed by: Professor António Parreira, Director of the Champalimaud Clinical Center & Daniela Cunha, Coordinator of the Champalimaud Clinical Center Dermatology Unit.