Unusual places you get melanoma
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Dr Mia Hugo enlightens us on the unusual places you can get melanoma.
A few years back, a patient gave me a great book: The Emperor of All Maladies: A biography of cancer. If cancer is the emperor, then melanoma is the spy who came in from the cold. Melanoma is the cloak and dagger tumour that can hide in plain sight as an innocent looking amelanotic melanoma to deeply hidden melanoma in the back of the eye or in the lining of the small intestine. I was reminded of all the strange places that one can find melanoma when a patient was referred to me for stereotactic radiation of a metastatic pelvic nodal mass that proved to be melanoma on biopsy, in whom the primary couldn’t be found.
Hiding in plain sight
Unusual skin presentations of melanoma
Acral lentiginous melanoma accounts for less than 5% of all skin melanomas but is the most common type of melanoma among darker-pigmented individuals. It starts mostly on the palms of the hands or
the soles of the feet or underneath the nails of a patient (subungual). Subungual melanoma arises from the nail matrix and usually presents as a longitudinal, brown or black band in the fingernail or toenail, with or without nail dystrophy.1
Amelanotic melanoma is far less common than clinically pigmented melanoma but presents a diagnostic challenge for patients and doctors. Lesions may present as pink or red macules, papules, or nodules, often with well-defined borders and frequently confused with non-cancerous (benign) lesions.1
Desmoplastic melanoma is a rare variant of melanoma. It presents as a slowly-growing plaque, nodule, or scar-like growth, and is usually non-pigmented (amelanotic) and located in chronically sun-exposed areas of older patients. It may clinically simulate a scar, other benign process, or non-melanoma skin cancer.1 Desmoplastic melanoma is locally aggressive with a propensity to recur and is one of the few melanoma subtypes that should be treated with adjuvant radiation. One of my favourite patients is a woman who had this culprit hiding in her hair. Now she rocks her hats and scarves and make us all laugh when she comes for follow-up.
Gone in the blink of an eye
Melanoma of the uvea or conjunctiva of the eye
Uveal melanomas are often asymptomatic, diagnosed on a routine eye exam while about half of uveal melanoma patients will present with visual symptoms, such as flashes, floaters, or visual field defects.
Oculodermal melanocytosis (ODM) is a congenital abnormality characterised by excessive melanocytes in and around the eye.2 ODM is the condition that most strongly predisposes to uveal melanoma, with a lifetime risk of approximately 1 in 400 of developing uveal melanoma.3 Radiation is the most common treatment for primary uveal melanoma in the form of plaque brachytherapy, particle therapy or stereotactic photon radiation.
Hide and seek
The mucosal epithelium lining the respiratory, alimentary, and genitourinary tracts all contain melanocytes and can give rise to melanoma.4 Mucosal melanomas are rare and form around 1.3% of melanoma in the USA. They are primarily found in the head and neck, anorectal, and vulvovaginal regions. Even rarer sites include the urinary tract, gallbladder, and small intestine.4 Vulvar melanomas represent 10% of all malignant tumours involving the vulva, while anorectal mucosal melanoma accounts for approximately 0.05% of colorectal and 1% of anal cancers.4
Malignant melanomas represent about 1 to 3% of all malignant tumours of the gastrointestinal tract, and while the majority of GIT melanoma are metastatic lesions, primary melanoma of the stomach or small bowel can occur.5
Mucosal melanomas can be asymptomatic initially and may present later with symptoms specific to the mucosal site. For example, nose bleeds, ill-fitting dentures, ulcerations, anaemia, itchiness, discharge, and pain.
Winning the cold war
While melanoma is notorious for sneaking up on patients and can hide in strange places, we just need to be vigilant and investigate any new symptoms or strange lesions to diagnose hidden melanomas. There are new effective strategies to combat it that have changed the landscape of melanoma treatment.
- Swetter, Susan and Geller, Alan. Melanoma: Clinical features and diagnosis. UpT0Date. [Online] 19 July 2022.
- Oculodermal Melanocytosis: Not to Be Overlooked. Luis A. Acaba-Berrocal, BA, Vladislav P. Bekerman, BS and Shields, and Carol L. October, s.l. : Ocular Oncology, 2017.
- J William Harbour, MDHelen A Shih,. Initial management of uveal and conjunctival melanomas. UpToDate. [Online] UpToDate, 31 August 2022. [Cited: 17 January 2023.]
- Carvajal, Richard D, Hamid, Omid and Ariyan, Charlotte. Locoregional mucosal melanoma: Epidemiology, clinical diagnosis, and treatment. UpToDate. [Online] 19 December 2022. [Cited: 17 January 2023.]
- Primary Small Bowel Melanoma: A Case Report and Review of Literature. Graças Amanda M., Souza Willy P., Canut Ana Carolina A., Franciss Maurice Y., Zilberstein Bruno. s.l. : Frontiers in Surgery, 2022, Vol. 9.
MEET THE EXPERT – Dr Mia Hugo
Dr Mia Hugo works in private practice as a radiation oncologist. She participates in weekly multi-disciplinary oncology team meetings for breast, urology, gastrointestinal/gynaecological, and head and neck cancers. She provides radiation to patients at Wits Donald Gordon, Netcare Milpark, Pinehaven and Olivedale Hospitals, as well as at Busamed and 200 Rivonia Medical Centre.
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