What's the most common kind of skin cancer?

June 12, 2019 / Duncan Fisher
Most skin cancers are carcinomas. That’s good news.

Carcinomas account for more than 80% of all skin cancers

The other skin cancers are either melanomas, so called because they usually arise in cells that contain the dark pigment, melanin, or they're one of the other non-melanomas, that include sarcomas and lymphomas. All of these are more dangerous than carcinomas, but they’re far less common.

The chances are, if you develop any kind of skin cancer at all, it will be a carcinoma. And carcinomas, generally speaking, are manageable.

Most carcinomas are either the deep-skin kind, called ‘basal cell’ carcinoma, and the outer-layer kind, called ‘squamous cell’ carcinoma.

Most people get the basal kind. And almost nobody dies of it. The squamous kind is more aggressive – the opposite of what you might expect, thinking about deep skin involvement versus shallow – and it is slightly more dangerous ... but only a little. Very few people die when they get this either.

If you receive absolutely no treatment for either of these carcinomas, and you wait a long time, and you’re very unlucky, it is possible that you can die. People do. But if you get to a doctor early, and if you’re generally healthy otherwise, there’s very little chance of either of these killing you.

But you should get to them early. And you should also know what to watch out for.

What carcinoma tends to look like

This is not a diagnostic manual. It takes a doctor to determine if you have cancer or not. And your doctor won’t determine this just by looking.

But looking is a useful place to start. There are visual symptoms that go with carcinoma often enough that they’re worth showing to your doctor if you see them. These don’t happen with every carcinoma, and some carcinomas, especially the basal kind, can be almost invisible. So don’t self-diagnose. But do be aware of ...

  • a sore that doesn’t want to heal
  • a reddish thickening of the skin, that may or may not itch
  • a discolored nodule, that might increase in size
  • an ulceration, that might itch, or might crust over

You’re absolutely right, if you look at this list and say, ‘I’ve had all those, and it’s never been cancer’. These features can signify lots of things. What you’re really looking for, in carcinoma, is localised changes, like these ones, that keep changing, and generally get worse. Having any of these signs doesn’t mean you have cancer, but it does mean, if the signs don't resolve, that it’s probably time to show a doctor.

Can you avoid a carcinoma?

You may hear health fanatics talk about ‘fighting cancer’ with diet, or with exercise, or mood-management. Cancer mechanisms are too complex, too varied, and too subtle for much of this to make sense.

But that doesn’t mean that lifestyle is irrelevant to cancer risk either. In the case of skin carcinomas, what seems to matter is sun exposure. More accurately, what matters is sun damage. The jury is still out on how much is too much, and what ‘damage’ means. But there really does seem to be a broad connection between sun and cancer.

What that connection is, is not clear yet. Suffice it to say that some wavelengths of the solar spectrum probably change the DNA in some of your skin cells, or else they change how your DNA expresses. It won’t happen the same to everybody, because some people – some families – simply don’t get cancer at the usual rate in the population. We don't know why. It’s like smoking and lung cancer: smoking doesn’t guarantee cancer, and non-smoking doesn’t guarantee no cancer. But statistically, more smoking and more cancer do go together. What’s actually happening, at the molecular level, is still being unwrapped.

So stay out of the sun. Do this assiduously if skin cancer runs in your family, or if you have fair skin. Never, ever go to a sunbed. If you’re immuno-compromised for any reason, be fanatical about sun exposure. You won’t be able to fight a little spread of rogue cells like you want. Healthy bodies suppress a lot of cancers before they even start. Yours may not.

What if you get a carcinoma?

If doctors see something that may be a carcinoma, they take it out. They send it to a pathology lab, where it’s sliced thin and dyed and examined under a microscope. If it’s cancer, the laboratory pathologists will see it there, and report back to your doctor. They’ll say what kind it is, and how far it appears to have spread. ‘Dermatopathology’ is quite developed, and they can do this.

If the pathologists think there are still cancerous cells around the excision site (they can tell this from the sample biopsy), your doctor will go back and get those leftover cells. This sounds dreadful, but it’s really microsurgery, and it’s not very deep. For basal cell excision they like to use ‘Mohs micrographic surgery’, a technique that’s now been around for decades, where they check for rogue cells minutely as they go. It’s a way of assuring clearance of bad cells and minimizing clearance of good cells. Basal cell carcinomas have a way of undermining your skin beneath what you can see. They spread laterally, and your doctor may well have to clear more cells, sometimes quite widely, much more than seemed necessary at first. (It's because basal cell carcinomas erode like this that you may hear them referred to as ‘rodent ulcers’.)

Excision isn’t always necessary, you'll be glad to know. For really trivial carcinomas, some doctors prescribe an immune response modifying cream, that has a marvelous record for making these little tumors vanish. You can ask your doctor about ‘imiquimod’, or other treatments like it.

There’s also focussed radiation treatment, and, surprisingly for a light-mediated disease, there’s light treatment, or ‘phototherapy’. These aren’t very common. They’re associated with advanced forms of carcinoma.

Almost always, in carcinoma, treatment is curative. You will still need to be followed up for a while, just to make sure that your carcinoma hadn’t already spread. Follow-up frequency and duration varies, depending on what you had, how big it had gotten, your general health and risk-exposure, and the treatment policy your doctor follows.

Chances are, there will be no recurrence. But if you got one cancer, the chances are also slightly elevated that you will develop another. That’s not because of the cancer itself – it’s because you may have a tendency to get this kind of cancer.

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