American Melanoma Institute · 5 min read
How cutaneous squamous cell carcinoma appears, what makes a tumor high risk, how doctors treat it, and what follow-up involves.
Cutaneous squamous cell carcinoma (SCC) is the second most common skin cancer. The American Cancer Society estimates that more than 1 million are diagnosed in the United States each year, about 2 of every 10 skin cancers. Most are cured with a minor procedure. A minority behave aggressively, and much of what your doctor does after the biopsy is aimed at finding out which kind you have.
SCC starts in squamous cells, the flat cells that make up most of the epidermis, the outer layer of skin. Long-term ultraviolet exposure is the main cause, which is why SCC favors the face, ears, lips, scalp, neck, forearms, backs of the hands, and lower legs.
The American Academy of Dermatology describes several forms: a rough, scaly patch, a firm dome-shaped bump, a sore that won't heal or that heals and returns, a wart-like growth, or a small horn of hard skin. The color may be pink, red, brown, black, or the same as the skin around it.
SCC often grows over weeks to months, faster than basal cell carcinoma, and many are tender or painful when pressed. It can also arise in old scars, burns, and long-standing wounds, inside the mouth, on the genitals, and around or under a nail. In Black people and people of Asian Indian heritage, SCC is the most common skin cancer, and it often appears in places that get little sun.
In situ is Latin for in place. SCC in situ means the abnormal cells fill the epidermis but have not broken through into the dermis, the thicker layer underneath that holds blood and lymph vessels. Without access to those vessels, the cells cannot spread through the body.
Bowen disease usually appears as a flat, red, scaly patch with a clear edge. People often treat it for months as eczema or ringworm before a biopsy gives the answer. Left alone, some patches progress to invasive SCC, so doctors treat them. Common choices include excision, curettage, freezing, fluorouracil or imiquimod cream, and photodynamic therapy.
Most SCCs never spread. When one does, it usually travels first to nearby lymph nodes. The American Cancer Society estimates that 4,000 to 9,000 people in the United States die of SCC each year, so doctors look hard for the features that flag a dangerous tumor. Current guidelines sort SCC into low-risk, high-risk, and very-high-risk groups.
Features that place a tumor in the high-risk group, as summarized by the American Cancer Society, include:
Very-high-risk tumors are wider than 4 cm, deeper than 6 mm or growing past the fat under the skin, poorly differentiated (the cells look very abnormal), invading nerves below the dermis, or entering blood or lymph vessels. Formal TNM staging, the system used for most cancers, applies only to SCCs of the head and neck.
Surgery is the standard. Options include excision with a margin of normal skin, curettage and electrodesiccation (scraping followed by cautery) for small, shallow tumors, and Mohs surgery. In Mohs surgery, the surgeon removes the cancer in thin layers and checks each under a microscope during the procedure, which gives the highest cure rate and saves the most normal tissue.
Radiation therapy is an alternative for people who can't have surgery. Creams and freezing are generally reserved for in situ disease.
High-risk SCCs are often reviewed by a team that includes a dermatologic or head and neck surgeon, a radiation oncologist, and a medical oncologist. Surgery with complete margin checking comes first when possible. Radiation may be added afterward if nerves were involved or margins were close.
Immunotherapy has changed care for SCC that cannot be cured with surgery or radiation. The American Cancer Society lists 3 checkpoint inhibitors, drugs that release a brake on immune cells, for advanced disease: cemiplimab (Libtayo), pembrolizumab (Keytruda), and cosibelimab (Unloxcyt). All are given through a vein every 3 to 6 weeks.
Cemiplimab now has 2 further roles, according to the American Cancer Society's August 2026 update. Doctors can give it after surgery and radiation to lower the chance of recurrence in higher-risk cases (adjuvant therapy), and they may give it before surgery to shrink a tumor (neoadjuvant therapy). Chemotherapy and drugs that target the EGFR protein remain options when immunotherapy is not suitable.
A typical follow-up visit includes a look at the scar, a full skin exam, and a check of the lymph nodes that drain the area. Visits are more frequent in the first few years. The schedule depends on the risk group, and people with suppressed immune systems are generally seen more often.
New skin cancers are common. DermNet reports that about 50% of people at high risk of SCC develop a second one within 5 years. Rough, sandpapery spots called actinic keratoses are the usual starting point for SCC, and treating them is one way dermatologists try to stay ahead of the next tumor.
