Squamous Cell Carcinoma

Squamous cell carcinoma is a form of non-melanoma skin cancer that begins in squamous cells, which make up much of the outer layer of the skin. Over time, ultraviolet radiation can damage the DNA within these cells. As this damage accumulates, abnormal cells may begin growing uncontrollably and eventually develop into skin cancer. SCC is particularly common on areas of the body that have received significant lifetime sun exposure, although it can develop almost anywhere on the skin.

Most squamous cell carcinomas are found early and successfully treated. However, SCC has a greater potential to behave aggressively than basal cell carcinoma. Some tumors can grow deeply into surrounding tissue and, in uncommon cases, spread to nearby lymph nodes or other parts of the body. The risk is not the same for every SCC, and factors such as the tumor’s size, location, depth, microscopic features, and the patient’s immune status can help determine whether an individual cancer is considered lower or higher risk.

Long-term exposure to ultraviolet radiation is the most important cause of cutaneous squamous cell carcinoma. Common risk factors include:

• Fair skin
• Significant lifetime sun exposure
• A history of frequent sunburns
• Indoor tanning bed use
• Increasing age
• Numerous actinic keratoses
• A weakened immune system
• Organ transplantation
• Previous radiation treatment
• A personal history of skin cancer
• Certain chronic wounds or scars

Although SCC is more common in older adults, it can occur at younger ages, particularly in people with substantial UV exposure or other risk factors.

Squamous cell carcinoma does not have one single appearance. It may look like a red, scaly bump; a firm or tender growth; a crusted or thickened spot; a rapidly growing bump; a sore that does not heal; or a lesion that repeatedly bleeds and forms a scab. Some SCCs have a wart-like appearance, while others begin as rough or scaly areas that gradually become thicker. Some are painful or tender, while others cause no symptoms at all. Any new, changing, growing, bleeding, or non-healing lesion should be evaluated by a dermatologist.

SCC frequently develops on chronically sun-exposed areas such as the face, ears, scalp, neck, lips, forearms, backs of the hands, and lower legs. However, squamous cell carcinoma can occur in areas that receive little or no sun exposure as well. Certain locations, including the ear and lip, can be associated with a greater risk of aggressive behavior and may influence treatment recommendations.

Actinic keratoses are rough or scaly areas caused by chronic sun damage and are considered precancerous lesions because a portion can eventually develop into squamous cell carcinoma. Patients with extensive sun damage may develop many actinic keratoses over time. Individual lesions can be treated with methods such as liquid nitrogen, while larger areas containing numerous precancerous changes may be treated with prescription creams, photodynamic therapy (PDT), or other “field treatments.” Having numerous actinic keratoses is also a sign of substantial cumulative UV damage and may indicate an increased risk of future skin cancers.

Diagnosis usually begins with an examination by a dermatologist. If a lesion appears suspicious, a skin biopsy is performed after numbing the area with local anesthetic. The tissue is then examined under a microscope to determine whether squamous cell carcinoma is present. The pathology report may also provide information about the type and characteristics of the tumor, which can help guide treatment.

Treatment depends on the tumor’s size, location, depth, microscopic characteristics, and other risk factors. Most SCCs can be treated very effectively with surgery, although several treatment options are available depending on the individual tumor.

Surgical Excision

Many squamous cell carcinomas can be treated with surgical excision. The cancer is removed along with a margin of surrounding normal-appearing skin, and the specimen is then examined to determine whether the tumor has been completely removed.

Mohs Micrographic Surgery

Mohs surgery may be recommended for SCCs that occur in certain high-risk or cosmetically sensitive locations, have aggressive features or poorly defined borders, or have previously been treated and returned. During Mohs surgery, the cancer is removed in stages and the surgical margins are examined during the procedure, allowing the surgeon to achieve a high cure rate while preserving as much healthy surrounding tissue as possible.

Cryosurgery or Curettage and Electrodesiccation

Certain small, superficial, low-risk squamous cell carcinomas may be treated by freezing or scraping/burning away the tumor and surrounding tissue. This approach is generally reserved for appropriately selected lesions in lower-risk locations.

Radiation Therapy

Radiation therapy may be considered when surgery is not appropriate or as part of the treatment of certain higher-risk tumors. The appropriate treatment should be individualized based on the characteristics of the cancer and the patient.

Squamous cell carcinoma in situ is the earliest form of SCC and is sometimes called Bowen disease. “In situ” means that the abnormal cancer cells remain confined to the uppermost layer of the skin and have not invaded more deeply. SCC in situ often appears as a persistent red, scaly patch and can resemble eczema, psoriasis, or another inflammatory rash. Because the cancer remains superficial, several treatments may be appropriate depending on its size and location, including surgical treatment, curettage and electrodesiccation, and certain topical therapies. Untreated SCC in situ can eventually progress to invasive squamous cell carcinoma, so treatment is generally recommended.

Yes, but most SCCs do not. The majority of cutaneous squamous cell carcinomas are successfully treated before they spread beyond the skin. However, the risk of recurrence or metastasis may be higher for tumors that are large or deeply invasive, occur in certain higher-risk locations, have returned after previous treatment, grow rapidly, have aggressive microscopic features, involve a nerve, or develop in a patient with significant immune suppression. Higher-risk tumors may require additional evaluation or closer follow-up. This potential to spread is an important distinction between SCC and basal cell carcinoma, which only very rarely metastasizes.

A previously treated SCC can occasionally recur in the same location. It is also common for patients with a history of SCC to develop an entirely new skin cancer somewhere else. A new cancer does not necessarily mean that the original cancer has spread; rather, a history of SCC indicates significant cumulative skin damage and an increased risk of developing additional skin cancers independently. This is why continued skin cancer surveillance remains important after treatment.

Follow-up should be individualized based on the characteristics of the cancer and the patient’s overall risk. Many patients with a history of squamous cell carcinoma benefit from full-body skin examinations every six to twelve months, while patients with multiple previous cancers, significant sun damage, immune suppression, or higher-risk SCCs may require more frequent follow-up. You should not wait for a scheduled examination if you notice a new, growing, bleeding, painful, or non-healing lesion.

Not every SCC can be prevented, but reducing ultraviolet exposure can help limit additional skin damage and reduce future risk. Helpful habits include:

• Using a broad-spectrum SPF 30 or higher sunscreen
• Reapplying sunscreen during prolonged outdoor activity and after swimming or sweating
• Wearing sun-protective clothing and wide-brimmed hats
• Seeking shade when possible
• Avoiding indoor tanning
• Performing regular self-skin examinations
• Treating precancerous actinic keratoses when appropriate
• Scheduling routine skin examinations with your dermatologist

Sun protection remains worthwhile even after decades of previous sun exposure.