Squamous Cell Carcinoma of the Skin

Actinic keratosis (AK), also known as solar keratosis, is a precancerous skin condition caused by too much exposure to the sun.

What AKs look like

AKs are usually small (less than 1/4 inch across), rough or scaly spots that are often flesh-colored or slightly darker, depending on a person’s skin tone.

Usually, they start on the face, ears, backs of the hands, and arms of middle-aged or older people with fair skin, although they can occur on other sun-exposed areas.

People who have AKs usually develop more than one. AKs tend to grow slowly and usually do not cause any symptoms, although some might be itchy or sore. They sometimes go away on their own, but they might come back.

Do AKs need to be treated?

A small percentage of AKs will turn into squamous cell skin cancers. Most AKs do not become cancer, but sometimes it can be hard for doctors to tell them apart from true skin cancers, so they often recommend treating them.

If you have AKs and they’re not treated, you and your doctor should check them regularly for changes that might be signs of skin cancer.

Squamous cell carcinoma in situ, also called Bowen disease, is the earliest form of squamous cell skin cancer. In situ means that the cells of these cancers are still only in the epidermis, the upper layer of the skin, and have not invaded deeper layers.

What Bowen disease looks like

Bowen disease typically appears as reddish patches. Compared with AKs, Bowen disease patches tend to be larger, redder, scalier, and sometimes crusted. Like AKs, Bowen disease usually doesn’t cause symptoms, although it might be itchy or sore.

Like most other skin cancers, Bowen disease most often appears in sun-exposed areas.

Bowen disease can also occur in the skin of the anal and genital areas. Some forms of SCC in situ in these areas have traditionally been called erythroplasia of Queyrat or Bowenoid papulosis. These can be related to infection with certain types of human papillomavirus (HPV).

Does Bowen disease need to be treated?

Bowen disease can sometimes progress to an invasive squamous cell skin cancer, so doctors usually recommend treating it.

People who have Bowen disease are also at higher risk for other skin cancers, so close follow-up with a doctor is important.

Keratoacanthomas (KAs) are dome-shaped tumors that often have an indent in the middle, like a volcano. These tumors tend to start on sun-exposed skin.

KAs might start out growing quickly, but their growth usually slows down. Many shrink or even go away on their own over time without any treatment. But some can continue to grow, and a few might even spread to other parts of the body.

Do KAs need to be treated?

Many doctors view keratoacanthomas as a type of SCC, although not all doctors agree. These tumors can be hard to tell apart from SCC just by looking at them, and their growth is often hard to predict, so doctors usually advise removing or destroying them, similar to how SCCs are treated.

Basal cell carcinoma (BCC), also called basal cell skin cancer or basal cell cancer, is the most common type of skin cancer. About 8 out of 10 skin cancers are basal cell carcinomas.

These cancers start in the basal cell layer, which is the lower part of the epidermis.

BCCs usually develop on sun-exposed areas, especially the face, head, neck, and arms. They tend to grow slowly. It’s very rare for a basal cell cancer to spread to other parts of the body. But if BCC is left untreated, it can grow into nearby areas and invade the bones or other tissues beneath the skin.

Learn more in Basal Cell Carcinoma.

These cancers develop from melanocytes, the pigment-making cells in the epidermis. Melanomas are much less common than basal and squamous cell cancers, but they are more likely to grow and spread if left untreated.

Learn more in Melanoma Skin Cancer.

Other types of skin cancer are much less common and are treated differently. These include:

• Merkel cell skin cancer
• Kaposi sarcoma
• Skin lymphoma
• Skin adnexal tumors – tumors that start in hair follicles or skin glands
• Various types of sarcomas

Together, these cancer types account for less than 1% of all skin cancers.