Quick Chat About Skin Cancer with Yale Dermatologist Sean Christensen

Skin cancer is the most common type of cancer in the United States, with millions of cases diagnosed each year. According to the National Institutes of Health (NIH), basal cell carcinoma and squamous cell carcinoma are the most frequently occurring forms, with over 4 million and 1 million cases annually, respectively. These cancers originate from the epidermis, the skin's outermost layer, and are primarily caused by ultraviolet (UV) radiation from the sun. While basal cell carcinoma tends to grow slowly and rarely spreads, squamous cell carcinoma can metastasize and be fatal in about 1% of cases if not treated promptly.

Melanoma, although less common, poses a greater threat due to its higher likelihood of spreading to other parts of the body. It arises from melanocytes, the cells responsible for skin pigmentation, and often manifests as a dark spot on the skin. Early detection is crucial for effective treatment.

Yale's comprehensive approach to skin cancer treatment combines expertise in Mohs surgery, multidisciplinary collaboration, and cutting-edge research to identify high-risk patients and implement preventative measures. This proactive strategy aims to reduce the incidence of skin cancer through early intervention and prevention efforts.

We caught up with Yale Medicine dermatologist Sean Christensen, MD, PhD, for a brief discussion about skin cancer, including treatments and prevention.

The responses below have been edited for space and clarity.

The epidermis is the outermost layer of skin that covers the entire body. Its primary function is to protect the body from environmental hazards like toxic chemicals and ultraviolet (UV) radiation from the sun. It also prevents essential fluids and nutrients from escaping through the skin. Despite being very thin (less than one millimeter thick), it is packed with cells that perform these protective duties.

The cells in the epidermis are called keratinocytes. They form a barrier to protect the body from the external environment. The basal layer is the deepest layer of the epidermis, where cells grow and divide to replenish the skin. Most skin cancers originate from cells in this basal layer.

Most skin cancers are caused by UV radiation from the sun, which penetrates the epidermis and damages cells in the basal layer. This damage causes mutations in the DNA of the cells, leading them to grow uncontrollably and potentially invade surrounding tissues. This unregulated growth is the hallmark of cancer.

The two most common types of skin cancer are basal cell carcinoma and squamous cell carcinoma, which are sometimes grouped together by the term non-melanoma skin cancer. Both of these originate in the epidermis but have different characteristics under the microscope. Basal cell carcinoma is the most common, with over 4 million cases annually in the U.S., while squamous cell carcinoma accounts for about 1 million cases. Both are primarily caused by UV radiation from the sun.

Basal cell carcinoma grows slowly and is unlikely to spread (metastasize) but can be very destructive if left untreated. Squamous cell carcinoma grows more quickly and has a metastasis rate of about 1% to 2%, making it potentially fatal in around 1% of cases. Both types are usually curable with surgery if detected early.

Melanoma is a more dangerous type of skin cancer that originates from melanocytes, the cells responsible for skin pigment. It often appears as a dark spot on the skin and is more likely to metastasize than basal or squamous cell carcinomas. Early detection is crucial for effective treatment.

Most skin cancers can be cured with surgical removal. For cancers in critical areas like the head, face, or hands, Mohs surgery is often preferred. Mohs surgery involves removing the cancerous tissue in stages and examining the edges under a microscope to ensure all cancer cells are removed while preserving as much healthy tissue as possible.

General prevention includes sun protection measures such as using sunscreen, wearing protective clothing, and avoiding excessive sun exposure. These simple measures reduce the damage to the epidermis caused by UV radiation and decrease the risk of skin cancer development. For high-risk patients with pre-existing sun damage, interventions like topical creams and light treatments can treat precancerous lesions and potentially prevent skin cancer.

Yale is researching ways to identify high-risk patients and apply active interventions, such as treating actinic keratosis with topical creams or photodynamic therapy. These measures aim to lower future skin cancer risks and are part of Yale's ongoing efforts to improve preventive care by pinpointing which patients will benefit most from these preventive treatments and implementing them effectively. This proactive approach helps in reducing the likelihood of skin cancer development, offering a significant advantage in patient care and long-term outcomes.