As we age, our skin acquires all sorts of mysterious lumps and bumps – some might be cancers, but most are benign. Here are some of the most common types that iToBoS will be learning to distinguish from melanoma. Article written by the Skin Cancer Genomics and Biomarker Discovery Group - Dermatology Research Centre - The University of Queensland Diamantina Institute.
Moles, or naevi, are the most common skin lesions, formed by a cluster of melanocytes, the skin’s pigment-producing cells. They can be brown, black, pink, the same colour as the surrounding skin, or even blue if the melanocytes are clustered deep in the inner layer of the skin. The number you have is partly controlled by genetics, but is also influenced by the amount of sun exposure and other environmental inputs.
Moles are harmless, but around 25% of melanomas arise in a mole and many more resemble moles in their early stages. To tell the difference, a doctor will usually check each mole with a dermoscope – a time-consuming process iToBoS plans to do away with by taking dermoscopy-level images of the whole skin in just a few minutes.
Seborrhoeic keratoses are another very common benign skin lesion and a normal part of the ageing process. The wart-like growths begin to appear in your 30s and 40s, and by the age of 60 around 90% of people will have at least one. They can be yellow, brown or black and often look as though they’ve been glued onto your skin.
Sometimes basal or squamous cell carcinomas arise within a pre-existing seborrhoeic keratosis, so your dermatologist will sometimes pay close attention to them. Seborrhoeic keratoses themselves are harmless but can be very numerous, and they increase in number as the years go by. This is a real problem for current state-of-the-art skin scanners, which have trouble separating them from moles when there is a high number of them.
Haemangiomas are another benign, usually painless skin lesion, formed from an overgrowth of blood vessels in the skin. They are usually firm lumps and can present as sharply defined, round bumps called cherry angiomas, round or oval lesions on the lip called venous lakes, or spider angiomas, which are cherry angiomas with red capillary lines wriggling out like spider legs. Depending on how deep in the skin they are, they can be red, purple or even deep blue.
Haemangiomas can mimic non-pigmented nodular melanomas, and having a history of melanoma is linked with having more haemangiomas, so iToBoS will be paying attention to these little red bumps.
Dermatofibromas are small, firm nodules, usually 1cm across or smaller, which are sometimes itchy and might be mistaken for an insect bite. They seem to be in the surface layer of the skin and, if you pinch one, a dimple will appear in it. On pale skin, they range from pink to light brown, and on darker skin from dark brown to black, and can be paler in the middle.
They are a benign proliferation of fibroblast cells (the main cells in connective tissue), perhaps in response to a mild skin injury. Several new dermatofibromas can appear if your immune system is suppressed. If they are ulcerated, have recently become bigger or are unusually coloured, your doctor needs to excise them to check they aren’t melanomas or basal cell carcinomas, so this is another lesion type for iToBoS to examine closely.