Dr Chris Irwin
If you’ve been diagnosed with a common skin cancer called SCC, this handout will help explain what that means in friendly, easy-to-understand terms. These skin cancers are very treatable, and are usually nothing like melanoma in terms of danger as long as treated properly.
We’ll explain what they are, how they’re treated, why additional tests are usually not needed, and what to expect going forward. The goal is to reassure you with facts: most SCCs are cured easily and rarely spread elsewhere.
Squamous cell carcinoma (SCC) is the second most common type of skin cancer (after BCC). It often appears as a scaly or crusty bump or patch on sun-exposed skin (face, ears, scalp, arms, or legs) and can sometimes ulcerate (form an open sore). SCC begins in the squamous cells of the epidermis (outer skin layer). These cells are the “bricks” that give the outer skin structure.
It tends to grow faster than BCC, but when found early it is highly curable and unlikely to spread. SCC is often divided into two categories based on how deep it goes: in situ (only in the top layer) and invasive (growing into deeper layers).
What is it? SCC in situ means the cancer cells are confined to the top layer of the skin (the epidermis) and have not invaded deeper layers. It’s also known as “Bowen’s disease” or “Intraepidermal carcinoma” (IEC). You might just see a persistent red, scaly patch that doesn’t heal – it can look like a rash or eczema patch.
In situ SCC is basically the earliest form of SCC (think of it as “stage 0” skin cancer). It grows very slowly over months to years and stays where it started. Because it hasn’t grown inward, it cannot spread (metastasize) to lymph nodes or other organs at this stage.
The skin contains two basic parts. The epidermis is the top layer of skin and the bottom layer of skin is called the dermis. The epidermis and dermis are separated by a very tough canvas like layer called the basement membrane or “dermo-epidermal junction”. If a cancer has not yet learnt how to get through this tough canvas layer, that means it has no way of travelling to other parts of the body (metastasis). This is because all of the highways that cancers use (eg. veins, arteries and lymph vessels) are all only in the dermis. There are no highways in the epidermis. This is great because it means if we treat it properly, the cancer can essentially be cured with no risk of metastasis and very low risk of recurrence.
The main concern is that, if left untreated, it could eventually turn into invasive SCC.
Risk of spread: By definition, in situ SCC has zero risk of having already spread elsewhere, since it hasn’t grown into the skin. However, if not treated, in situ lesions can become invasive over time. Because of this chance of progression, doctors recommend treating Bowen’s disease so it doesn’t get the chance to turn into an invasive SCC. The good news is that once it’s treated, it’s essentially cured and no longer poses a threat.
Treatments: SCC in situ is usually easy to treat with minor procedures or topical (skin-applied) therapies.
Common treatments include:
All of these methods have good cure rates for in situ SCC. Your doctor will recommend the method that best fits the size, location, and your preference. Sometimes a treated area might need a repeat treatment if it wasn’t completely cleared the first time – or a different method – but this is not usually a big concern, as Bowen’s disease is very controllable.
Are lymph node biopsies or scans needed? No – not for in situ SCC. Because it has not invaded the skin, there is virtually zero chance of spread to lymph nodes or elsewhere at this stage. Therefore, no CT scans or lymph node biopsies are indicated for isolated SCC in situ. Your doctor likely won’t order any extra tests besides maybe a skin biopsy (to diagnose it in the first place). The focus is just on treating the patch on the skin.
When are further tests considered? For SCC in situ, further tests aren’t needed.
Outlook: The outlook for SCC in situ is excellent. Once treated, it is usually cured outright. Bowen’s disease itself is not life-threatening. The main goal is preventing progression to invasive SCC, and treatment achieves that in the vast majority of cases. We do recommend keeping an eye on your skin and having regular check-ups (see Follow-Up Care at the end) because having Bowen’s disease can be a sign of sun damage, and you might develop other skin cancers or another patch in the future. Should the same spot not fully respond to treatment or if it comes back, your doctor will simply treat it again. Bottom line: SCC in situ is highly curable and seldom causes serious problems.
What is it? Invasive SCC means the cancer cells have grown deeper into the skin beyond the epidermis. This is what doctors often simply call “squamous cell carcinoma.” It’s no longer confined to the top layer. Invasive SCC usually appears as a firm red or skin-colored bump or a crusty, scaly nodule. It might ulcerate (get a sore in the middle) or bleed, especially if bumped. Common locations are sun-exposed areas like the face (especially lips), ears, bald scalp, neck, arms, and hands. These tumors can also arise in old scars or chronic wounds. Invasive SCC can grow outward and inward, and if neglected it can become a fairly large sore. The good news is that most SCCs are found when they are still fairly small (often less than 2 cm) and have not spread anywhere else.
How is it treated? The main treatment is to remove the tumor. Because it has grown into the skin, a slightly more robust treatment than for in situ is needed. Typical treatment approaches for invasive SCC include:
Why no extensive scans or tests in most cases? Unlike many internal cancers, a routine invasive SCC doesn’t require CT scans, PET scans, or a bunch of blood tests.
This is because in most cases (especially small, early SCCs), the chance that it has spread beyond the skin is extremely low. The doctor will do a thorough skin exam and feel the nearby lymph nodes during your exam – that’s typically sufficient. If the SCC is caught early and removed completely, that’s usually the end of the story (apart from follow-up skin checks). There is no need to put you through unnecessary scans that are unlikely to show anything.
Prognosis and follow-up: The cure rate for invasive SCC is very high, especially when caught early. A small SCC removed with proper margins has a cure rate around 95% or higher.
In cases where an SCC does come back or spread, it usually happens within the first 2-3 years, which is why your doctor will schedule follow-up skin exams.
Importantly, even though invasive SCC can be more serious than BCC, in most typical situations it is still very manageable and unlikely to ever be life-threatening. We emphasize sun protection and regular check-ups because people who have had one SCC might develop another new one in the future (sun-damaged skin can pop out multiple cancers over time). But with vigilance, these can be caught early and treated easily as well.
In summary, invasive SCC is usually cured with a simple outpatient procedure, and only in rare higher-risk cases do we need to consider more extensive monitoring or treatment. The overall outlook is excellent for the majority of patients.
The Skin Doctor is a leading centre for cosmetic and medical skin treatments, including the diagnosis and treatment of skin cancers.