Melanocytes are pigmented skin cells that are located in the deep layers of the skin (epidermis).…
Squamous cell carcinoma
What is squamous cell carcinoma?
Squamous cell carcinoma (SCC) is a type of skin cancer that originates in the squamous cells forming the outer layer of the skin. When squamous cell carcinoma occurs in locations such as the mouth, tongue and throat, it is usually named after the location (i.e. mouth cancer). Squamous cell carcinoma occurs when abnormal squamous cells grow uncontrollably in the skin. Occasionally, these abnormal cells can spread beyond the top layer of the skin to the deeper tissues and, rarely, to distant sites in the body.
The cause of skin cancer, as with other cancers, is damage to cellular DNA. This damage results in uncontrolled growth of damaged cells, leading to tumour formation. This damage to skin cells is a result of exposure to ultraviolet (UV) radiation, which can come from sunlight, but also solariums and tanning beds. The intensity of the UV radiation and the time and pattern of exposure to it, all combine to affect the risk of cancer development.
You may be at higher risk of squamous cell carcinoma if any of the following apply to you:
- Age - the risk of skin cancer increases with age;
- UV radiation exposure - intense exposure that leads to sunburn, or accumulative exposure, such as working outdoors;
- Smoking - specific for squamous cell carcinoma of the lips;
- Tanning - using sun beds and solariums;
- Family history of squamous cell carcinoma;
- A weakened immune system, and;
- Fair skin.
Treatment outcomes can vary greatly depending on the stage of cancer. Squamous cell carcinoma is staged according to the size and spread of the original tumour in the nearby area and whether the cancer has spread to other parts of the body, such as lymph nodes and organs.
This is also called Bowen's disease, or carcinoma in situ. It refers to the presence of cancerous cells that are contained to their place of origin, in this case the skin.
The cancer is 2cm or less in size and has one or none of the following features: it is more than 2mm thick, has grown into the lower layer of the skin, is near a nerve, started on the ear or lip, or looks very abnormal under a microscope.
The cancer is greater than 2cm and has two or more of the following features: it has grown into the lower layer of the skin, is near a nerve, started on the ear or lip, or looks very abnormal under a microscope.
The cancer has spread to a lymph node on the same side of the body and this lymph node is less than 3cm in size, or the cancer has invaded the bones of the face.
The cancer has spread to a lymph node on the same side of the body and this lymph node is greater than 3cm, or has spread to multiple lymph nodes on either side of the body, or throughout the body to other sites.
Signs and symptoms
Squamous cell carcinoma can appear as a flat reddish patch that grows slowly, or a rough bump on the skin that can be dome-shaped and crusty. Squamous cell carcinoma is generally slow-growing and frequently forms an ulcer that will not heal. Some squamous cell carcinomas begin as pre-cancerous growths called actinic keratosis, which appear as small, pink, itchy, scaly patches.
Methods for diagnosis
Your doctor will examine the abnormal skin section and, if there are any concerns about the cells being potentially cancerous, will perform further tests.
A biopsy is a tissue sample taken for microscopic examination in the laboratory. A local anaesthetic is often used during biopsies, but this depends on the size of the sample to be removed. Your doctor will choose the best type of biopsy and recommend if an anaesthetic is required. There are three main types of skin biopsies:
- Incisional biopsies, which involve the removal of the entire abnormal area of skin with a scalpel;
- Punch biopsies, which involve the removal of a small circle of the whole skin layer, much like a hole puncher removes holes in paper, and;
- Shave biopsies, which involve shaving off the top layer of skin.
Types of treatment
Treatment usually involves removal of the cancer at the site where it developed. In the vast majority of cases, this provides the cure.
This is the surgical removal of the abnormal tissue. It is usually performed as a minor procedure, in which a cut is made around the cancer and all the tissue containing cancerous cells is removed.
Liquid nitrogen is used to freeze-kill abnormal cells.
Mohs' micrographic surgery
The skin is removed one layer at a time and immediately examined under a microscope for cancer. Layers are removed until no trace of cancer is found.
Electrodessication and curettage
Electrodessication and curettage is a simple surgical technique used to remove smaller squamous cell carcinomas. It involves using an instrument called a curette, which looks like a spoon with a sharp edge, to remove the tissue. This is followed by electrodessication, which uses a needle electrode to apply an electric current to the tissue to stop (cauterise) any bleeding.
Radiation therapy uses focused X-rays to destroy cancerous cells and is most commonly used in the treatment of large squamous cell carcinomas, or in situations where the tumour has spread. As the radiation beams hit normal tissue as well as cancerous tissue, radiation therapy is associated with some side effects. For example, radiation directed at the mouth can cause damage to the salivary glands, which then leads to a dry mouth and dental problems.
Chemotherapy works by attacking cancer cells and stopping their reproduction. Various medications are used, which can be administered either intravenously or orally. Chemotherapy is generally only used for cancers that are very large, or that have spread from the original site of the tumour.
Side effects occur because chemotherapy can also affect the growth of healthy cells. Your doctor will monitor such side effects and choose the most appropriate dose and type of medication for your situation.
There is ongoing research into the use of biological therapies for the treatment of squamous cell carcinoma. These drugs target receptors that are involved in regulating the growth of cancer cells. Biological therapies can block this process, inhibiting the growth of the cancer.
Some people diagnosed with cancer seek out complementary and alternative therapies. None of these alternative therapies are proven to cure cancer, but some can help people feel better when used together with conventional medical treatment. It is important to discuss any treatments with your doctor before starting them.
Treatment side effects
In rare cases when the squamous cell carcinoma has spread throughout the body, requiring the use of systemic chemotherapy, side effects potentially include fatigue, nausea and vomiting. Other side effects may be associated with particular agents.
This is when the cancer spreads to other parts of the body through the bloodstream and lymphatic system, affecting the vital function of organs. This is very uncommon in the case of squamous cell carcinoma.
Prognosis varies according to the stage of the cancer. Squamous cell carcinoma generally has an excellent prognosis, as metastases are uncommon. Based on this, your doctor will discuss further treatment details suitable for your situation.
The best way to prevent skin cancer is by minimising your exposure to UV radiation, which can be done by avoiding sunlight during the times specific to your state, [1 ] seeking out shade and wearing protective clothing, such as hats and long-sleeved shirts with collars, to protect the arms and neck. Avoiding suntanning and tanning beds is one of the easiest things you can do to help lower your risk.
If you are at high risk of developing squamous cell carcinoma - for instance, if you are taking medications for long-term suppression of your immune system or have had many squamous cell carcinomas in the past - your doctor may talk to you about other means of prevention. Vitamin A derivatives, called retinoids, have been shown to be effective in prevention of development of new squamous cell carcinomas.