Squamous cell carcinoma is the second most common skin cancer. It usually appears as a rough, scaly or crusted bump on skin that has had years of sun, and it often looks like a sore that will not heal. Found early it is removed and cured. Left alone it grows deeper, and a small share spread. An actinic keratosis is a rough, scaly patch caused by years of sun. It is a precancer, meaning it is the step before skin cancer rather than cancer itself. Most never progress, but most squamous cell carcinomas start as one, which is why they are treated.
The same eight facts on every condition comparison.
It is a skin cancer of keratinocytes.
It arises from the main cells of the outer skin.
It often looks crusted or ulcerated.
It may be a growing scaly lump, persistent sore or tender patch.
Most are treated successfully.
Some can invade deeply or spread to lymph nodes.
Risk is assessed individually.
Size, depth, site and immune status guide care.
It is ultraviolet damage.
Actinic keratoses are rough, scaly areas caused by UV damage to skin cells.
It appears on sun-exposed skin.
They occur most often on repeatedly exposed areas.
It is precancerous.
Some can progress to squamous cell carcinoma.
Some lesions need a biopsy.
Thick, painful, ulcerated or enlarging spots are checked for invasive cancer.
Squamous cell carcinoma in situ Flat red scaly patch, surface only.
Invasive squamous cell carcinoma Generated illustration. Firm, crusted or ulcerated bump.
Keratoacanthoma Fast-growing dome with a central crater.
Classic actinic keratosis Rough pink or red scaly spot.
Hypertrophic actinic keratosis Thick, raised and crusted.
Actinic cheilitis Rough, dry patches on the lower lip.
Pigmented actinic keratosis Brown and flat.
DNA changes allow abnormal surface skin cells to multiply, commonly after long-term ultraviolet damage. In invasive squamous cell carcinoma, the cancer grows through the epidermal boundary into the dermis.
Repeated ultraviolet exposure damages the DNA of surface skin cells, allowing abnormal cells to grow within the epidermis. A rough, scaly patch develops, and some lesions can progress to skin cancer.
Squamous Cell Carcinoma. Usually appears in older adults after cumulative sun damage; immunosuppression can lead to earlier disease.
Actinic Keratosis. Usually develops in adults after years of ultraviolet exposure, especially with fair or immunosuppressed skin.
Squamous cell carcinoma starts when DNA damage makes skin cells grow out of control. Ultraviolet light is the main cause.
Actinic keratoses are caused by years of ultraviolet light damaging skin cells. They are a warning sign of sun damage.
Fair skin that burns easily is inherited and raises the risk.
Fair skin that burns easily is inherited and is the biggest risk.
Evidence labels come from each condition’s own treatment list.
An over-the-counter form of vitamin B3, taken as a tablet, which modestly reduced new actinic keratoses and new skin cancers in people at high risk. The effect is real but small, and it stops when the tablets stop. It is an add-on to sun protection and treatment, not a replacement for either. Check with your doctor before starting it.
The lower lip is the site almost nobody protects and one of the higher-risk places for a patch to progress. A balm with SPF 30 or higher, reapplied through the day, is the practical way to cover it. It will not treat a lip that is already persistently dry, scaly or cracked — that needs looking at.
Fluorouracil cream (5-FU). The best-studied cream for treating a whole sun-damaged area rather than single spots, usually applied for two to four weeks. It attacks abnormal cells wherever they are, so it also clears patches that had not surfaced yet. The area becomes red, crusted and sore where those cells were, often revealing more than you knew you had — that reaction is the treatment working, and stopping early leaves the area half treated. If you are pregnant or breastfeeding, ask the doctor managing your pregnancy first.
Imiquimod cream. Prompts your own immune system to clear the abnormal cells, applied a few times a week over a longer course than fluorouracil. It also treats the whole field, and it can suit the face and scalp well. Expect redness and crusting, and sometimes a few days of feeling fluey. The same pregnancy advice applies: ask the doctor managing your pregnancy first.
Tirbanibulin ointment. A newer ointment used once a day for five days on the face or scalp. The short course and the milder reaction are the point of it — most people are through the redness and flaking within a couple of weeks. It is used on a limited area at a time, and long-term results are less well known than for fluorouracil.
An anti-inflammatory gel applied twice a day for two to three months. It is much gentler than fluorouracil, which makes it an option for people who cannot manage a strong reaction on visible skin. It clears fewer patches, and the course is long.
A prescription retinoid people often ask about here, because it is known for sun-damaged skin. It smooths texture and helps the mottled color, but trials have not shown that it clears actinic keratoses or prevents skin cancer. It is reasonable for the look of sun damage, and it is not a treatment for the patches themselves.
An oral retinoid used mainly for organ transplant recipients and others whose immune systems are suppressed, who make large numbers of these patches and progress from them more often. It reduces how many new patches and skin cancers appear while it is taken, and the benefit fades once it is stopped. It has real side effects and needs blood tests. It must never be taken in pregnancy, and pregnancy has to be avoided for three years afterwards.
The tumor is removed a layer at a time and each layer is checked under the microscope during the same appointment, so the surgeon stops as soon as the edges are clear. It gives the highest cure rate and takes the least normal skin, which is why it is used on the face, ears, lips, hands, feet and genitals, and for large, recurrent or aggressive tumors. It is a long appointment rather than a difficult one.
The standard removal: the tumor is cut out with a margin of normal skin around it and the wound is stitched closed, usually in one visit under local anesthetic. It cures the large majority of straightforward tumors on the trunk, arms and legs. The margins are checked afterwards rather than during, so occasionally a second procedure is needed to clear an edge.
The tumor is scraped out with a small loop and the base is sealed with an electric current, repeated a few times in one sitting. It is quick and effective for small, thin, low-risk tumors on the trunk and limbs. It is not used on the face, on large or recurrent tumors, or anywhere depth matters, because nothing is sent for margin checking and it leaves a round pale scar.
A quick freeze in clinic, used for actinic keratoses and occasionally for a small patch of carcinoma in situ. It is a treatment for the step before this cancer, not for the cancer itself. Freezing an invasive tumor leaves cells behind at depth and hides what is happening under a healing crust.
A light-activated cream treatment for the earliest forms only — actinic keratoses and some cases of carcinoma in situ. It treats a whole patch of sun-damaged skin at once and heals with a good cosmetic result. It has no role in an invasive tumor, and using it on one delays proper removal.
Nothing else on this page happens without it. Even an experienced dermatologist with a dermatoscope cannot settle this by looking, and the report says far more than yes or no — how deep it goes, how aggressive the cells look, whether it is tracking along a nerve. Those details choose the treatment. It takes a few minutes under local anesthetic and leaves a small wound. A biopsy does not make cancer spread.
The thicker, harder patches that freezing struggles with are scraped away under local anesthetic and the base sealed. It is useful when a patch has built up into a lump or a horn, and the scraped material can be sent for testing. It leaves a small scar, and like freezing it treats only the spot in front of you.
Freezing with liquid nitrogen is the quickest option for a handful of separate patches, done in a few seconds each with no prescription. It stings sharply, then blisters or crusts and heals over one to three weeks. Its limit is that it only treats what can be seen, so new patches keep arriving from the damaged skin around them. It often leaves a permanently pale mark, which is more noticeable on deeper skin tones — worth asking about before you start.
A light-activated liquid is put on the whole area, left to soak in, then activated with a lamp. It treats a broad field in one or two clinic visits instead of weeks of cream, which suits people who cannot manage a long course at home. The area stings during treatment and is red, swollen and sore for several days, and the treated skin has to be kept out of light straight afterwards.
Not a treatment, but the right answer for a patch that is thick, firm, tender, bleeding, growing quickly, bigger than about a centimeter, forming a horn, sitting on the lip or ear, or unchanged after proper treatment. A few minutes under local anesthetic tells you whether the abnormal cells are still confined to the top layer or have gone deeper. Freezing a patch like that instead removes the evidence without answering the question.
A medium-depth peel takes off the damaged top layer across a whole face or scalp at once, so it treats the field rather than single spots. It is an option when creams have not been tolerated. The skin is red and peeling for about a week, and results depend a lot on who is doing it and at what strength.
Most skin squamous cell carcinomas are cured with appropriate treatment, but they should not be left untreated. Some grow or spread more quickly, especially with immune suppression. Follow-up helps detect recurrence and additional skin cancers.
Actinic keratoses are not steady. Individual spots come and go, which is one reason they get dismissed. The trend over years is upward.
A small percentage reach the lymph nodes
A small percentage spread to nearby lymph nodes and occasionally further. Higher risk with large or deep tumors, ear or lip sites, recurrence, and immunosuppression.
Squamous Cell Carcinoma
The skin cancer that these patches can turn into. Any one patch is unlikely to progress in any one year, but most squamous cell carcinomas begin in an actinic keratosis or in the damaged skin around one, and people usually have many patches over many years. Treating patches lowers how many of these appear later. A patch that thickens, hurts, itches, bleeds or grows quickly is sampled rather than frozen.
Actinic cheilitis on the lip
The same sun damage on the lower lip, where it shows up as persistent dryness, scaling, cracking or a lip border that has blurred into the skin. It is easy to read as chapped lips, and lip balm does not fix it. The lip matters more than its appearance suggests, because it is a higher-risk site if a patch progresses, so a dry scaly lower lip that has not settled in a month should be looked at.
Arrange prompt assessment of a persistent scaly, crusted, enlarging or non-healing lesion, especially if tender or bleeding.
Arrange assessment of persistent rough spots. Rapid growth, tenderness, thickening, ulceration or bleeding raises concern for skin cancer.
It is a real cancer and treated as one. Most cases are cured by removal, which is why the emphasis is on early checks. Untreated, it grows into deeper structures and a small share reach lymph nodes. How serious it gets depends on how long it is left.
Usually weeks to months rather than days or years. The keratoacanthoma variant can appear and enlarge within a few weeks. In immunosuppressed people growth can be much faster, which is why the advice for that group is more urgent.
It depends on the site and how the tumor looks under the microscope. Mohs is generally used on the face, ears, lips, hands, feet and genitals, and for large, recurrent or aggressive tumors. Tumors on the trunk, arms and legs usually get a standard excision.
The treated one can recur, though that is uncommon when margins were clear. Far more common is a new skin cancer elsewhere, because the same damage runs through the rest of the skin. Hence follow-up after a cure.
It substantially raises the odds - many people who have one keratinocyte cancer develop another within a few years. Hence skin checks, daily sun protection and treating actinic keratoses.
Most people do not. Scans and node assessment are reserved for high-risk features - large size, deep invasion, growth along nerves, recurrence, immunosuppression - or an enlarged node. Your dermatologist decides from the pathology report and examination.
No. It is a precancer - abnormal cells in the top layer of skin that have not formed a tumor. A minority become squamous cell carcinoma, and they are treated because most squamous cell carcinomas begin this way.
Low, for any single patch in any single year. Published estimates vary too widely to quote. What matters is cumulative: more patches, for longer, with more sun. A suppressed immune system raises it considerably.
It stings for a few seconds and aches afterward. It blisters or crusts within a day or two and heals over one to three weeks. A pale mark often remains where the skin regrows with less pigment - sometimes permanent, and more noticeable on deeper skin tones.
That is how it works. Fluorouracil and imiquimod provoke a reaction exactly where abnormal cells are, so the area turns red, crusted and sore, often revealing more patches than you knew you had. It settles a couple of weeks after finishing. Stopping early leaves the area partly treated.
New ones almost certainly will, because the sun damage remains. That is not treatment failure. Most people settle into periodic checks, occasional retreatment and daily sun protection - the protection is what reduces how many new ones appear.
A few discrete patches, and freezing is efficient. Many patches, or a whole area of damaged skin, and a cream or photodynamic therapy lasts longer, because it reaches cells that have not surfaced yet. Downtime is part of the choice.
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