What Is Squamous Cell Carcinoma

The skin is the largest part of our body acting as a barrier in protecting us from bacteria, chemicals, temperature and other elements. Though it is a protective layer for us, overexposure to certain factors like ultraviolet light (UV) or excessive tanning under sunlight can disrupt the skin. One such extreme skin disruption is squamous cell carcinoma (SCC), a type of non-melanoma skin cancer. In the UK among the diagnosed skin cancer cases, 23% is found to be SCC occurring in individuals above the age of 75. With early detection and treatment, SCC patients showed positive prognoses.^1,2

Read on to know more about what is squamous cell carcinoma, its causes, its indicative signs and symptoms, and current treatment and management strategies. 

Overview

Squamous cell carcinoma (SCC) is a commonly occurring type of skin cancer that arises from thin squamous cells flat cells that make up the outermost layer (epidermis) of the skin. SCC typically develops on parts of your body that are exposed to the sun the most, such as your face, head, arms, and legs. Actinic keratoses (a pre-cancerous growth), a dry scaly path of the skin caused due to prolonged sun exposure is seen as one the causes of SCC that develop tumours and spread throughout the body.³

SCC usually appears as a firm, red, scaly patch with slightly raised growth or barely visible in certain cases which could be mistaken for sunburn. Although SCC commonly occurs in areas exposed to the sun, there is still a possibility of SCC developing the mucus membrane that coats the interior of organs and bodily cavities like the lungs, mouth, or anus.^3,4

Based on the cellular differences and the location of cancer, squamous cell carcinoma (SCC), is divided into different types. Some of the common types of SCC include:^3,4,5

1. Squamous cell carcinoma in situ (SCCIS): Also known as Cutaneous squamous cell carcinoma or Bowen's disease, is a non-invasive type of SCC that remains on the top layer of the skin. SCCIS may appear as a red, scaly patch or a raised bump that grows slowly over time, but if left untreated it can spread into deeper layers of the skin
2. Invasive/metastatic SCC: One of the most common types of SCC, which results in cancerous tumours that invade deeper layers of the skin and can spread to organs and lymph nodes in the body if left untreated
3. Verrucous carcinoma: This is a rare subtype of SCC that usually occurs in the mouth (considered oral cancer) and occasionally in the feet or genital area (considered skin cancer). It occurs on the skin with a sore or wart-like appearance and tends to grow slowly. Verrucous carcinoma is less aggressive than invasive SCC and has a better prognosis if treated early on
4. Adenoid SCC: Adenoid SCC is another rare type of SCC that has a cyst-like appearance that may mimic a non-cancerous cyst or tumour. It usually occurs in sun-exposed areas like the head and neck. Adenoid SCC is more aggressive than conventional SCC and is treated differently

It is important to keep an eye on any wound, sore or wart on your skin in general but if it does not heal visit your GP or dermatologist to get it examined. The earlier you get treated for any sores or ulcers it will help reduce the chances of squamous cell carcinoma. 

Causes of squamous cell carcinoma

Squamous cell carcinoma develops in a person due to multiple factors. SCC develops gradually in a person due to prior extensive sun exposure, skin injuries and so on. 

SCC growth may be influenced by several factors, such as:^3,4,4,6

• Sun exposure: The most frequent cause of SCC is exposure to ultraviolet (UV) radiation from the sun or artificial sources, including tanning beds. The genetic component (DNA) present in the skin cells becomes damaged, which causes the cells to become cancerous
• Genetic mutation: The genetic chances (mutation) occurring to the gene p53 induced by ultraviolet (UV) exposure is one of the main causes of squamous cell carcinoma. When the p53 gene is mutated, the healthy cells lose their normal division function. This causes your squamous cells to overproduce and over-duplicate, which causes tumours to form both internally and externally
• Age: SCC is more prevalent in older people (75 years and above) because of exposure to the sun and other external conditions over an extended period of time. This might raise the chance of generating cancerous mutations
• Fair skin: Although a person with any skin colour can develop SCC, the risk of developing SCC is higher in those with fair skin, light-coloured hair, and eyes because they are more vulnerable to UV-induced skin damage due to the lack of pigment (melanin)
• People with weakened immune systems: People with HIV/AIDS or who have undergone an organ transplant have weak immune systems. They are at increased risk for SCC due to their immune system’s reduced ability to fight off cancerous cells
• Exposure to certain chemicals and smoking: SCC risk has been related to prolonged exposure to chemicals like arsenic, which can be present in some pesticides and drinking water. Due to the presence of cancer-causing substances like tar in cigarettes, smoking has been associated with an increased risk of SCC, particularly in the lips and mouth
• Previous skin damage: SCC can develop from pre-existing skin conditions, such as severe sunburns (exposed to UV radiation), chronic wounds due to human papillomavirus (HPV), unhealed scars, or sores. A precancerous lesion due to actinic keratosis or Bowen's disease can increase one’s risk to develop SCC

If you have a familial history of skin cancers or are diagnosed with a rare genetic disease, xeroderma pigmentosum (severe sensitivity to sunlight) will put you at a higher risk of developing squamous cell carcinoma. It is essential to remember that not everyone who gets SCC has a recognised risk factor, but if you are prone to SCC talk with your GP to learn about precautionary steps. 

Signs and symptoms of squamous cell carcinoma

Squamous cell carcinoma (SCC) can occur in many ways, depending on location, size of the tumour, the severity of spread and so on. The scalp, hands, ears, and lips are some of the sun-exposed body parts where squamous cell carcinoma most commonly occurs. Yet, it may occur anywhere on your body, including the inside of your mouth, the soles of your feet, and your genitalia.³ 

Some common signs and symptoms that indicate the presence of SCC are:^3,5,6

• Presence of scaly, red, or rough patch of skin that does not heal: Skin that is rough or scaly and has a red, pink, or brown colour might be a sign of SCC. This patch can be raised or flat, and with time, it might bleed or start to get crusty
• A raised firm bump: SCC can also develop as a firm or hard to the touch, elevated (raised above the skin but sinks in the middle) lump or nodule. This kind of lesion may have a rough, scaly surface and over time may bleed or develop into an ulcer
• A sore or ulcer that does not heal: An open sore or ulcer that does not heal over several weeks can be an indication of SCC. This type of sore may be painful, tender, or itchy, and it may crust or bleed
• Changes in a pre-existing skin condition or sore: SCC can also develop from a pre-existing skin growth, such as a mole, wart or dome-shaped growth, that changes in size, shape, colour, or texture over time. This type of lesion should be examined by a dermatologist, as it can be an indication of skin cancer
• Other symptoms: A spot on your lower lip where the skin turns pale, dried out, and cracked known as cheilitis (severely chapped lips) can occur. When exposed to the sun, this might cause a burning feeling. In some cases, white or light stains on your cheeks, tongue, gums, or in your mouth known as leukoplakia can also occur. SCC can occasionally result in additional symptoms including numbness, tingling, or a lack of sensation in the affected region, particularly if the tumour has spread to nearby nerves or other tissues

It is crucial to remember that, not all skin sores, burns or unhealed wounds are cancerous, and some SCCs may not even exhibit any symptoms. But if you see any changes in your skin or have unhealed wounds, it's important to have it checked out by a doctor because early diagnosis and treatment will increase the chance of a positive outcome.

Management and treatment for squamous cell carcinoma

Squamous cell carcinoma (SCC) management and therapy mainly rely on the location, size of the tumour, age and as well as the patient's general health. The main goal of the treatment is to completely eradicate the cancerous tumour from one’s body through minor surgery and other accompanying treatments. 

The current management and treatment strategies for SCC are:^3,4,5,6

• Surgical excision: Surgery excision, which involves removing the tumour and a small amount of surrounding tissue to avoid future spread or reoccurrence, is the most popular form of therapy for SCC. According to the size and location of the tumour, this is normally carried out under local anaesthetic, and the surgical wound may either be stitched shut or allowed to heal naturally
• Cryotherapy: Cryotherapy may be an option for extremely small SCC tumours. Liquid nitrogen is used in cryotherapy to freeze the tumour, which results in the killing of the cancerous cells
• Mohs micrographic surgery: SCCs that are big or located in hard-to-treat regions, such as the face or genitalia, are frequently treated with this specialised surgical method. In Mohs surgery, small layers of tissue are taken out one at a time, and they are then examined under a microscope to make sure that all of the cancerous cells have been removed
• Chemotherapy: Topical chemotherapeutic creams (such as 5-fluorouracil) may be prescribed for minor SCCs and only present on the skin surface. It is often used in combination with electrodesiccation with curettage ( C&E: scratching and burning the small tumour surgically) or photodynamic therapy
• Photodynamic therapy (PDT): This involves applying a photosensitizing agent to the skin, which is then activated with a blue light. The activated substance destroys cancer cells while protecting healthy tissue
• Other therapies: Radiation therapy may be used in combination with surgery to kill any remaining cancer cells or to shrink large tumours before surgery. Laser therapy using an intense beam of light to vaporise small and surface-level tumours is used in combination with chemotherapeutic creams

Regular follow-up appointments with a dermatologist or oncologist are important to check for the recurrence or development of new tumours. It is important to follow protective steps such as periodic application of sunscreen, wearing protective clothing, and staying out of the sun for long periods when undergoing treatment and recovery.³

FAQs

How is squamous cell carcinoma diagnosed?

Dermatologists typically use a biopsy to analyse a sample of abnormal skin tissue under a microscope to diagnose SCC. Depending on the size and location of the lesion, the biopsy may be done by shaving, punching, or excisional techniques. Further imaging tests (CT or MRI) maybe be done to see if SCC is spread further underneath the skin.⁶

How can I prevent squamous cell carcinoma?

The best way to prevent SCC is by protecting your skin from UV radiation by using (reapplying every 2 hours) a broad-spectrum sunscreen with SPF 30 or higher, staying in the shade, wearing protective clothing, hats, and sunglasses and avoiding tanning beds. Moreover, you should regularly examine your skin and visit a GP or dermatologist if you find any unusual unhealed wounds or moles.^3,6

Who are at risk of developing squamous cell carcinoma

A person is more likely to develop SCC if they have a history of prolonged sun exposure, sunburns, tanning, a compromised immune system, exposure to certain chemicals or radiation, fair skin or a personal or family history of skin cancer.³

How common is squamous cell carcinoma

SCC is the second most common type of skin cancer, accounting for about 20% of all cases. In the UK 23% of all skin cancer cases are SCC and seen in people above 75 years.^1,2,3

What types of squamous cell carcinoma are there

Squamous cell carcinoma (SCC) has several subtypes, including Squamous cell carcinoma in situ (SCCIS), invasive/metastatic SCC, verrucous carcinoma, and adenoid SCC. These subtypes vary in appearance, location, and manner of development.^3,4,5

When should I see a doctor?

You should see a doctor if you notice any unusual changes in your skin, such as new bumps or lumps on your skin, changes in the colour or texture of existing moles or wounds, or any signs of redness, itching or bleeding. These changes may be due to other medical conditions, hence it should be examined by a GP for an accurate diagnosis.

Summary

Squamous cell carcinoma (SCC), is a type of non-melanoma skin cancer that occurs in the outermost layer of the skin (epidermis) containing squamous cells. It commonly develops as patchy bumps or lumps in areas which are overexposed to the sun such as the face, scalp and neck, but it can occur in other regions containing squamous cells such as the mouth, lungs or anus. The primary cause of SCC is due to extensive ultraviolet (UV) exposure leading to the mutation of the p53 gene accompanied by other factors such as age, exposure to chemicals, smoking, fair skin or people with weak immune systems. 

It is easily treatable when caught early, hence it’s important to check your skin regularly for any new moles or unhealed sores. SCC is preventable to an extent when prevention measures such as regular application of sunscreen, avoiding the use of tanning beds and prolonged sun exposure. Talk with your GP if you or your family has a history of skin cancer, so you can adopt precautionary measures.