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Skin Cancer

  • Cancer that develop in skin cells
  • Types include melanoma, basal cell cancer, squamous cell cancer, Merkel cell carcinoma, Kaposi sarcoma, lymphoma of the skin
  • Treatments include excision, Mohs surgery, radiation therapy, and medications
  • Involves dermatology, dermatologic surgery, cutaneous oncology program, melanoma program, dermatopathology

Skin Cancer


While you may enjoy your time in the sun, bear in mind that skin cancer is caused by ultraviolet light that comes from the sun’s rays. Over time, sunlight exposure can cause damage to the DNA of the skin.

“While anybody can develop skin cancer, people with lightly colored eyes, hair, and skin and who have a family history of skin cancer are at increased risk,” says David J. Leffell, MD, chief of Dermatologic Surgery and Cutaneous Oncology at Yale Medicine. Repeated exposure to the sun is another risk, which can affect people who work outdoors. Having experienced blistering sunburns in childhood is another risk for developing skin cancer, he says, which can take years to surface.

At Yale Medicine, experts diagnose and treat all forms of skin cancer—both melanoma and non-melanoma skin cancer—using the most advanced techniques. Because our doctors are also scientists, they perform research to advance the understanding of skin cancers and their treatment. 

What are the major kinds of skin cancer?

There two main types of skin cancer: melanoma and non-melanoma (which includes basal and squamous cell) skin cancers. Here in the United States, non-melanoma skin cancers are more common than melanoma. However, skin cancer rates in general are on the rise.

What is a melanoma?

Melanomas are the rarest of the three main types of skin cancer, but they are also the deadliest. Although melanoma usually results from sun exposure, it can occur in areas of the skin that have never seen sunlight. Besides sun damage, risk factors for melanoma include family history of skin cancer, the number of moles (typical and atypical) a person may have on their skin and other unknown causes.

One type of melanoma is melanoma in-situ (Stage 0 melanoma). This is a type of melanoma that affects the top layer of skin only—the epidermis—and has not spread into the deeper layers of skin. 

What are non-melanoma skin cancers?

There are two main types of non-melanoma skin cancer:

  • Basal cell cancer (BCC)—Also known as basal cell carcinoma, it begins in the basal cells of the skin. It is the most common type of non-melanoma skin cancer. It often appears as a transparent, clear bump on the skin that grows slowly and may bleed. 
  • Squamous cell cancer (SCC)—Also called squamous cell carcinoma, it begins in the squamous cells of the skin. It presents as thick, crusty growths that are raised and firm.

Are there other kinds of skin cancer?

There are other, rarer forms of skin cancers as well: 

  • Cutaneous T-cell lymphoma (CTCL). CTCL is not linked to sun exposure but is a rare type of lymphoma that affects the skin, blood, lymph nodes, and internal organs. It appears as small patches of red, dry skin that spread slowly over time. The cancer can spread to the bloodstream, lymph nodes, and internal organs. 
  • Merkel cell carcinoma (MCC). This is typically a fast-growing cancer that affect the cells in the upper layer of the skin, which are called Merkel cells. 
  • Kaposi sarcoma (KS). A rare form of cancer that can cause tumors to form under the skin, in lymph nodes, or on mucosal surfaces such as the mouth and nose.

What are the risks for skin cancer?

The main risks include the following: 

  • Having light skin, eyes, and hair
  • Repeated sun exposure
  • Family history of skin cancer
  • Organ transplantation. Special medications used to prevent organ-transplant rejection reduce your immune system's ability repair DNA damage or eliminate cells that could develop into skin cancer.

How are skin cancers diagnosed?

During a physical exam, a dermatologist will identify bumps or growths that may be cancerous and perform a skin biopsy, if necessary, to learn more. A skin biopsy is a quick, in-office procedure. The area of concern is numbed with a local anesthetic, and a small tissue sample is removed. It is then evaluated under a microscope by a dermatopathologist (skin pathologist) who will determine if the growth is malignant (cancerous) or benign (noncancerous). Biopsy results come back in about a week or so.

How is skin cancer treated?

If you are diagnosed with skin cancer, doctors have a variety of ways to remove cancerous cells from the skin so that they do not spread (or continue to spread) to other healthy tissues. The main treatments include the following:

  • Excision: Skin cancers, large or small, can be removed surgically—the cancer is cut out and the area is then stitched during an operation.
  • Mohs micrographic surgery (MMS): This procedure is used to treat basal cell and squamous cell skin cancers. In MMS, the surgeon removes the cancer layer by layer, and the layer of tissue is examined under a microscope after each step, so the dermatologist can confirm that all of the cancer cells have been eliminated. It maximizes the chances of removing all of the abnormal cells while still preserving as much of the normal skin tissue as possible. MMS has a high cure rate for both basal cell and squamous cell skin cancers. 
  • Radiation therapy:  In radiation therapy, an external beam of radiation is targeted precisely at a skin cancer to kill cancerous cells. It is used for patients with non-melanoma skin cancer who are not healthy enough for surgery or who cannot have surgery for other reasons, and in cases in which the cancer occurs in places where surgery would be difficult such as the corner of an eye, in the nostrils or on an earlobe.  It is also sometimes used after surgery to ensure that any cancer cells that remain are destroyed. Radiation therapy may be an option for people with metastatic cancer (cancer that has spread to other parts of the body). In these cases, radiation may be a palliative measure, meaning it is not used to cure the disease, but instead to relieve pain and other symptoms.
  • Medications: There are several medications available now for basal cell cancer that is inoperable and squamous cell cancer of the skin that has spread to other parts of the body. They are not used for routine skin cancers, which represent the vast majority of skin cancers that are diagnosed.

How can you minimize your risk of skin cancer?

Dr. Leffell suggests the following:

  • Avoid sunburns.
  • Apply a high-SPF sunscreen (30 or higher).
  • Reapply sunscreen every two hours or more frequently when swimming or perspiring.  
  • Wear a wide-brimmed hat to shade your face.
  • Avoid time in the sun during peak hours, between 10 a.m. and 4 p.m. 
  • Avoid tanning beds.
  • Give yourself a skin exam every month to look for new growths. Anything new, that has changed in color or size, or that’s asymmetrical, peeling, bleeding, or not healing—should be evaluated by a dermatologist. 

What is unique about Yale Medicine’s approach to skin cancers?

Our doctors are experts in treating skin cancers using the latest techniques. Whether you have one skin cancer or many, our dermatolog­­­­ic surgeons have expertise in treating skin affected by multiple cancers. The Dermatologic Surgery & Cutaneous Oncology Program is one of the largest of its kind in the country. We are also internationally known for our treatment of rare cancers such as cutaneous T-cell lymphoma. 

“Yale Medicine Dermatology is known for its expertise in skin cancer and melanoma,” says Dr. Leffell. “A major feature is our patient-centered approach in the office setting, which has been embraced by patients for more than three decades.”