There are 3 common types of cancer, although there are many types of rare skin cancer. The 3 common types – BASAL CELL CARCINOMA (BCC), SQUAMOUS CELL CARCINOMA (SCC) and MALIGNANT MELANOMA (MM) – are all very different in behaviour and who they usually affect.
BCC and SCC usually affect older people. They are often associated with sun exposure, although BCCs may occur in areas of the skin where there is prolonged immune suppression, such as the lower legs when there is long-term venous eczema.
BCCs spread locally but very, very rarely do they spread beyond the point where they arise (they don’t METASTASISE as the medical jargon has it). That doesn’t mean they’re not dangerous, because they are inexorable. They grow and grow to incredible size if not treated, SO GET THEM SEEN EARLY. They may invade bone, and blood vessels, and eat away at the body. There are some shocking examples of what they can do in medical museums. There are different types of BCC – low risk types (superficial and nodular) and high risk types (because their edges are difficult to identify clinically – morphoeic and micronodular). Superficial BCCs can be treated by cream, other types by surgery or radiotherapy, both of which have both advantage and disadvantages.
SCCs can spread from the original site (but also invade locally as BCCs do) and so are more dangerous. They usually spread to local LYMPH GLANDS or NODES; in the case of the leg, those are in the groin, arm (armpit, aka AXILLA), head (neck). It is more common for people to die from SCC although it is still rare in the UK.
MM can affect the young as well as the old, and are much more worrying. They can be very difficult for pathologists to identify (the pathologists often say that MM can look like anything. They don’t have to be very advanced to spread; far-flung deposits can show up years after the original lesion has been treated and all-but-forgotten. They made spread to the liver, lungs or anywhere (another old saw of doctors is to ‘beware the patient with the false eye and the big liver) because an MM of the eye (yes, it can occur in the eye) treated by its removal may result in liver deposits years later.