Skin cancer, the abnormal growth of skin cells, is the most common type of cancer among both men and women and is diagnosed more than all other cancers combined. Nearly 6 million people will be diagnosed with nonmelanoma skin cancer this year in the United States, while an additional 180,000 will be diagnosed with melanoma. There are three major types of skin cancer- basal cell carcinoma, squamous cell carcinoma and melanoma.
Skin cancer develops primarily on areas of sun-exposed skin, including the scalp, face, lips, ears, neck, chest, arms and hands, and on the legs in women. But it can also form on areas that rarely see the light of day including palms, beneath the fingernails or toenails, and the genital area. Skin cancer affects people of all skin tones, including those with darker complexions. When melanoma occurs in people with dark skin tones, it’s more likely to occur in areas not normally exposed to the sun, such as the palms of the hands and soles of the feet.
Basal cell carcinoma usually occurs in sun-exposed areas of the body, such as the neck or face. These areas may appear as a pearly or waxy bump or a flat, flesh-colored or brown scar-like lesion.
Most often, squamous cell carcinoma occurs on sun-exposed areas of the body, such as the face, ears and hands. People with darker skin are more likely to develop squamous cell carcinoma on areas that aren’t often exposed to the sun. These areas of skin may appear as a firm, red nodule or a flat lesion with a scaly, crusted surface.
Melanoma can develop anywhere on the body, in otherwise normal skin or in an existing mole that becomes cancerous. In men, it most often appears on the face or the trunk; while in women, this type of cancer most often develops on the lower legs. In both men and women, melanoma can occur on skin that hasn’t been exposed to the sun. Melanoma can affect people of any skin tone. In people with darker skin tones, it tends to occur on the palms or soles, or under the fingernails or toenails. Signs of melanoma include:
- A large brownish spot with darker speckles.
- A mole that changes in color, size or feel or that bleeds.
- A small lesion with an irregular border and portions that appear red, white, blue or blue-black.
- Dark lesions on the palms, soles, fingertips or toes, or on mucous membranes lining the mouth, nose, vagina or anus.
Other, less common types of skin cancer include:
- Kaposi sarcoma. This rare form of skin cancer develops in the skin’s blood vessels and causes red or purple patches on the skin or mucous membranes. It mainly occurs in people with weakened immune systems, such as people with AIDS, and in people taking medications that suppress their natural immunity, such as people who’ve undergone organ transplants. Other people with an increased risk of Kaposi sarcoma include young men living in Africa or older men of Italian or Eastern European Jewish heritage.
- Merkel cell carcinoma. Merkel cell carcinoma causes firm, shiny nodules that occur on or just beneath the skin and in hair follicles. Merkel cell carcinoma is most often found on the head, neck and trunk.
- Sebaceous gland carcinoma. This uncommon and aggressive cancer originates in the oil glands in the skin. Sebaceous gland carcinomas, which usually appear as hard, painless nodules, can develop anywhere, but most occur on the eyelid, where they’re frequently mistaken for other eyelid problems.
Skin cancer begins in the skin’s top layer called the epidermis. The epidermis is a thin layer that provides a protective cover of skin cells that the body continually sheds. The epidermis contains three main types of cells:
- Squamous cells- lie just below the outer surface and function as the skin’s inner lining.
- Basal cells- produce new skin cells and sit beneath the squamous cells.
- Melanocytes– produce melanin, the pigment that gives skin its normal color, are located in the lower part of the epidermis. Melanocytes produce more melanin when in the sun to help protect the deeper layers of the skin.
Where the skin cancer begins determines its type and a patient’s treatment options.
Much of the damage to DNA in skin cells results from ultraviolet (UV) radiation found in sunlight and in the lights used in tanning beds. But sun exposure doesn’t explain skin cancers that develop on skin not ordinarily exposed to sunlight. Here are risk factors to consider for all types of skin cancer:
- Fair skin- having less pigment (melanin) in the skin, and having blonde or red hair and light-colored eyes, freckles or skin that sunburns easily will also increase the risk.
- A history of sunburns- having had one or more blistering sunburns as a child or teenager increases the risk of developing skin cancer as an adult. Sunburns in adulthood also are a risk factor.
- Excessive sun exposure- including exposure to tanning lamps and beds.
- Sunny or high-altitude climates- living in sunny, warm climates has more exposure to sunlight. Those living at higher elevations, where the sunlight is strongest, are exposed to more radiation.
- Moles- having many moles or abnormal moles, which look irregular and are generally larger than normal moles. Abnormal moles are more likely than others to become cancerous.
- Precancerous skin lesions- these precancerous skin growths, called actinic keratoses, typically appear as rough, scaly patches that range in color from brown to dark pink. They’re most common on the face, head and hands of fair-skinned people whose skin has been sun damaged.
- A family history of skin cancer- from a parent or sibling.
- A personal history of skin cancer- if skin cancer has developed once, it’s more likely to develop again.
- A weakened immune system- including those living with HIV/AIDS and those taking immunosuppressant drugs after an organ transplant.
- Exposure to radiation treatment- for skin conditions such as eczema and acne may have an increased risk of skin cancer, particularly basal cell carcinoma.
- Exposure to certain substances- such as arsenic.
- Being male- men have in increased risk for developing melanoma.
Luckily, most types of skin cancers are preventable. Sun safety prevention tips are to wear sunscreen all year round, wear protective clothing, avoid the sun during the middle of the day, avoid tanning beds, be aware of sun-sensitizing medications, and check your skin regularly and report any changes to your physician or dermatologist.
If skin cancer is suspected, a skin biopsy will be performed. Because superficial skin cancers such as basal cell carcinoma rarely spread, a biopsy which removes the entire growth often is the only test needed to determine the cancer stage. But for a large squamous cell carcinoma, Merkel cell carcinoma or melanoma, a doctor may recommend further tests to determine the extent of the cancer. Additional tests might include imaging tests to examine the nearby lymph nodes for signs of cancer or a procedure to remove a nearby lymph node and test it for signs of cancer (sentinel lymph node biopsy).
Surgery is a common treatment for basal cell and squamous cell skin cancers through different surgical techniques. The options depend on the type of skin cancer, how large the cancer is, where it is on the body, and other factors. Most often the surgery can be done in a doctor’s office or hospital clinic using a local anesthetic (numbing medicine). For skin cancers with a high risk of spreading, surgery sometimes will be followed by other treatments, such as radiation or chemotherapy. Some forms of surgery include:
- Excision– The tumor is then cut out with a surgical knife, along with some surrounding normal skin. The remaining skin is carefully stitched back together, which will leave a scar.
- Curettage and electrodesiccation– Removal of the cancer by scraping it with a long, thin instrument with a sharp looped edge on one end (called a curette). The area is then treated with an electric needle (electrode) to destroy any remaining cancer cells. This process is often repeated once or twice during the same office visit. Curettage and electrodesiccation is a good treatment for superficial (confined to the top layer of skin) basal cell and squamous cell cancers. It will leave a scar.
- Mohs surgery (microscopically controlled surgery)- Often used when there is a high risk the skin cancer will come back after treatment, when the extent of the skin cancer is not known, or when the goal is to save as much healthy skin as possible, such as with cancers near the eye or other critical areas such as the central face, ears or fingers. The Mohs procedure is done by a surgeon with special training. First, the surgeon removes a very thin layer of the skin (including the tumor) and then checks the removed sample under a microscope. If cancer cells are seen, another layer is removed and examined. This is repeated until the skin samples are free of cancer cells. This is a slow process, often taking several hours, but it means that more normal skin near the tumor can be saved. This can help the area look better after surgery.
- Lymph node surgery– Recommended if lymph nodes near a squamous or basal cell skin cancer are enlarged. Sometimes, many nodes might be removed in a more extensive operation called a lymph node dissection. The nodes are then looked at under a microscope for signs of cancer. This type of operation is more extensive than surgery on the skin and is usually done while a patient is under general anesthesia.
- Skin grafting and reconstructive surgery– After surgery to remove a large basal or squamous cell skin cancer, it may not be possible to stretch the nearby skin enough to stitch the edges of the wound together. In these cases, healthy skin can be taken from another part of the body and grafted over the wound to help it heal and to restore the appearance of the affected area.
While most skin cancers are not life threatening, melanoma is the most serious and potentially harmful type of skin cancer. Once a melanoma diagnosis has been made, the next step in a treatment plan is to determine how serious the cancer is and if it’s spread to other areas of the body, this is called staging. To determine the appropriate stage, there are three things to consider- the size of the tumor, if it’s spread to nearby lymph nodes and if it has spread to distant sites. The stages for melanoma are as follows:
Stage 0- The melanoma cells are found only in the outer layer of skin cells and have not invaded deeper tissues.
Stage I- The tumor is no more than 1 millimeter thick and the outer layer of skin may appear scraped (ulceration). OR, the tumor is between 1 and 2 millimeters thick and there is no ulceration and the melanoma cells have not spread to nearby lymph nodes.
Stage II: The tumor is between 1 and 2 millimeters thick and there is ulceration. OR, the thickness of the tumor is more than 2 millimeters, there may be ulceration and the melanoma cells have not spread to nearby lymph nodes.
Stage III: The melanoma cells have spread to one or more nearby lymph nodes. OR, the melanoma cells have spread to tissues just outside the original tumor but not to any lymph nodes.
Stage IV: The melanoma cells have spread to other organs, to lymph nodes, or to skin areas far away from the original tumor, such as the lungs, liver or brain.
Recurrent: Recurrent disease means that the cancer has come back (recurred) after it has been treated. It may have come back in the original site or in another part of the body.
Surgery is the main treatment option for most melanomas, and usually cures early-stage melanomas. Wide excision differs from a skin biopsy in that the margins are wider because the diagnosis is already known. The recommended margins vary depending on the thickness of the tumor. Thicker tumors need larger margins (both at the edges and in the depth of the excision). In some situations, Mohs surgery might be an option (explained above), however this type of surgery is used more often for other types of skin cancer. Amputation is uncommon but needed in some situations where the melanoma is on a finger or toe and has grown deeply, then part or all of that digit might need to be amputated.
If the lymph nodes are not enlarged, a sentinel lymph node biopsy may be done, particularly if the melanoma is thicker than 1 mm. If the sentinel lymph node does not contain cancer, then there is no need for a lymph node dissection because it’s unlikely the melanoma has spread to the lymph nodes. If the sentinel lymph node contains cancer cells, removing the remaining lymph nodes in that area with a lymph node dissection is usually advised. This is called a completion lymph node dissection.
If melanoma has spread (metastasized) from the skin to other organs such as the lungs or brain, the cancer is very unlikely to be curable by surgery. Even when only 1 or 2 areas of spread are found by imaging tests such as CT or MRI scans, there are likely to be others that are too small to be found by these scans. Surgery is sometimes done in these circumstances, but the goal is usually to try to control the cancer rather than to cure it. If 1 or even a few metastases are present and can be removed completely, this surgery may help some people live longer. Removing metastases in some places, such as the brain, might also help prevent or relieve symptoms and improve a person’s quality of life.
In most cases, a treatment plan of chemotherapy and/or radiation therapy will be used before, after or in combination with surgery.
Immunotherapy is the use of medicines to stimulate a person’s own immune system to recognize and destroy cancer cells more effectively. Several types of immunotherapy can be used to treat melanoma, including immune checkpoint inhibitors such as PD-1 inhibitors and CTLA-4 inhibitors.
Targeted therapies have also proven effective for melanoma treatment, including BRAF inhibitors, MEK inhibitors and drugs that target cells with C-KIT gene changes. Targeted drugs work differently from standard chemotherapy drugs, and sometimes work when chemotherapy doesn’t. They can also have less severe side effects.