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Skin Cancer

Skin cancer is the most diagnosed malignancy across the world. Though most cases are preventable, skin cancer can greatly affect the quality of life, and can even cause death. The yearly incidence of skin cancer is higher than that of all other cancers combined. In India, skin cancers account for about 1-2% of all diagnosed cancers. Exposure to direct sunlight is related to the risk of the development of skin cancers. Despite awareness and screening measures, the increased rates of skin cancer raise concerns for both patients and the healthcare system. 

About skin cancer

The skin is the largest organ in the body. It has a discrete structure and is made up of mainly three layers: epidermis, dermis, and hypodermis. The skin primarily acts as a physical and biological barrier against irritants, allergens, and the external environment. Additionally, it prevents the loss of water and helps maintain internal homeostasis.

Skin cancer occurs when the normal skin cells undergo mutations (changes) in their DNA and begin to grow out of control. These abnormal changes in the cells may initially lead to a pre-cancerous stage.  In some cases, these pre-cancers cells turn into invasive cancers that can spread to other parts of the body and can be fatal.

Types of skin cancer

The main types of skin cancers are:

• Basal cell carcinoma: It accounts for 80 percent of skin cancers. This cancer begins in the basal cell lining that lies beneath the squamous layer. They usually grow slowly and rarely spread to other parts of the body.
• Squamous cell carcinoma: It accounts for 20 percent of all skin cancers. This cancer begins in the squamous cells that make up the middle and outer layers of the skin. They often develop in the sun-exposed areas such as the ears, face, scalp, neck, and hands. They grow rapidly and spread to other parts of the body.
• Melanoma: It develops from melanocytes, the skin cells that produce melanin pigment, which gives skin its color. They resemble moles and can be found on any area of the body, even in areas that are not typically exposed to the sun.
• Merkel cell cancer: It is rare, aggressive skin cancer. It develops in the hormone-producing cells just beneath the skin and in the hair follicles. Merkel cancers usually appear as firm, painless lesions, or nodules on sun-exposed areas.

Signs and symptoms

Abnormal changes or lesions in the skin are the warning signs of skin cancers.

The signs and symptoms of each type of skin cancer are usually different, such as:

• Squamous cell carcinomas may produce a wart-like and scaly skin lesion with a depression (ulcer) in the center. 
• Basal cell carcinomas may produce white, or flesh-colored, dome-like lumps with a waxy appearance.
• Melanomas often include a new or existing mole that has irregular borders or elevation that changes in size, shape, color, or appearance.

Causes/Risk factors

Though the exact cause of skin cancer is not clear, the ultraviolet (UV) radiation found in sunlight and the lights used in tanning beds is found to increase the risk of skin cancer. Intense exposure and cumulative, long-term exposure to UV radiation may damage the skin cells leading to cancer.

Factors that might increase the risk of skin cancer include the following:

• A family history of skin cancer
• A personal history of skin cancer
• Weakened immune system
• Intense exposure to radiations
• Fair skin
• Precancerous skin lesions
• A history of sunburns or fragile skin
• A Large number of moles

Skin Cancer Diagnosis

Initially, the signs and symptoms, medical history, and family history of the patient are reviewed. Based on the appearance of the skin lesion, a biopsy of the suspicious skin area may be recommended to confirm the diagnosis.

Biopsy: A sample of tissue is collected from the suspected area and is examined under the microscope to determine any abnormalities. A biopsy can be done in one of the several ways, including:

• Shave biopsy is often recommended when a basal cell or squamous cell carcinoma is suspected. The procedure involves shaving off a piece of the lesion by numbing that area.
• Excisional biopsy is usually recommended when melanoma is suspected. The procedure involves numbing the entire suspected and surrounding tissue and removing the entire tumor for analysis.
• Incisional biopsy is similar to an excisional biopsy, but during the procedure, only a portion of the tumor is removed for laboratory analysis.

When skin cancer is confirmed through biopsy, other imaging tests like computerized tomography (CT) scan or magnetic resonance imaging (MRI) scans may be recommended to determine whether the skin cancer has spread to other body parts.

Stages of skin cancer

Basal cell and squamous cell carcinomas rarely spread to other parts of the body. The melanoma staging is done using the TNM staging system. It provides detailed information about:

• Tumour (T): Whether the primary tumor is located and how thick or deep is the original tumor
• Node (N): Whether cancer has spread to the lymph nodes surrounding the tumor
• Metastasis (M): Whether cancer has spread to distant parts of the body

The staging for skin cancer includes:

• Stage 0a/0is: Tumors are located only in the top layers of the skin and have not spread to the surrounding tissues.
• Stage I: Tumors are either smaller than 0.8mm and are not ulcerated or between 1 and 2 mm in thickness but not ulcerated.
• Stage II: Tumors are either between 1 to 4 mm in thickness and ulcerated and/or more than 4 millimeters in thickness but not ulcerated or greater than 4 millimeters thick and are ulcerated.
• Stage III: Tumor may be of any thickness and may or may not be ulcerated, but the tumor has spread to nearby lymph nodes
• Stage IV: The tumor can be any size and has spread through the bloodstream to other parts of the body like the lungs, liver, or bones.

Skin Cancer Treatment

Based on the type of skin cancer, its stage, size, and location, the patient can be treated with the following treatment modalities: 

Surgery: It is the mainstay of treatment for both melanoma and non-melanoma skin cancers. Depending upon the type, size, and stage of cancer, any of the following surgeries may be recommended:

• Cryosurgery: It is a type of ablation to destroy the cancerous cervical tissues at cold temperatures. During the procedure, a liquid nitrogen probe is placed directly on the tumor cells to freeze and destroy the growth on the surface of the skin. It is an effective treatment for precancerous skin lesions (for actinic keratosis treatment).
• Mohs micrographic surgery: It is an effective method for removing basal and squamous cell carcinomas. During the procedure, the tumor growth is removed layer by layer, and examined under the microscope, until no cancer cells remain. This procedure involves removing the cancerous cells while preserving the healthy surrounding tissues.
• Excisional surgery: It is the main melanoma cure, and involves the removal of the tumor and some surrounding healthy skin and soft tissues. The extent of the surgery depends on the size and thickness of the tumor.
• Curettage and electrodesiccation: It is usually recommended for very small basal cell and squamous cell carcinomas. The procedure involves the removal of the skin lesion with a curette, which is a sharp, spoon-shaped instrument. It is followed by treating the area with an electric current to control bleeding and destroy the remaining cancer cells.
• Sentinel lymph node biopsy: It is recommended for advanced-stage cancers that have spread to the lymph nodes. The procedure involves identifying the affected lymph nodes and removing the entire suspected area and surrounding tissues.

Radiation therapy: It involves the use of high-energy X-ray beams to kill cancer cells. It is usually recommended for advanced-stage skin cancers and for tumors that cannot be completely removed during surgery. For skin cancers, radiation therapy is given either externally by using an external machine or internally by placing a radioactive substance near the tumor.

Chemotherapy: It involves the use of potent drugs to destroy rapidly growing cancer cells in the body. These drugs interfere with the process of cell division and promote cancer cell death. In cancers that are limited to the top layer of skin, these drugs are applied topically (directly to the skin). For advanced cancers, chemo drugs are injected into a vein (IV).

Targeted therapy: Targeted therapy involves the use of specific drugs to identify and destroy skin cancer without causing much damage to the normal cells. These drugs are used to treat melanoma and some non-melanoma skin cancers, and also in rare cases of advanced basal cell carcinoma treatment.

Immunotherapy: It involves the use of certain medicines to boost a person’s immune system to find and destroy the cancer cells. Checkpoint inhibitors and cytokines are two classes of immunotherapy drugs that are used to treat some cases of Merkel cell carcinoma and melanoma.

Preventive measures

Even though, there is no proven way to completely prevent skin cancers, managing some risk factors may help in lowering the risk of the disease.

 

Follow these steps to prevent skin cancer:

• Get regular skin cancer screenings.
• Wear sunscreen.
• Avoid tanning beds.
• Limit or avoid direct exposure to the sun during the middle of the day.
• Wear sun-protective clothing.

Outlook

When detected and treated early, non-melanoma skin cancers can have a survival rate above 95 percent. These cancers can be completely removed by surgery. The prognosis of malignant melanoma depends on the thickness of the tumor at the time of treatment. The survival rate decreases for advanced-stage skin cancers, when cancer has metastasized to other areas of the body.