Squamous cell carcinoma is the second most common type of skin cancer. It begins in the outermost layer of the skin, known as the epidermis.

Squamous cells are one of the three main types of cells in the epidermis. They are flat and located near the surface of the epidermis. Squamous cell carcinoma (SCC) occurs when genetically mutated cells grow at an accelerated rate and do not die as they should. The mutated cells then have the potential to invade local structures and metastasize to distant sites.

The incidence rate of this type of skin cancer has increased by 200% in the last 30 years. Research estimates that there are 1.8 million new cases every year.

Keep reading to learn more about cutaneous SCC, including pictures, the causes and risk factors, as well as information on diagnosis and treatment options.

SCC of the skin is also called cutaneous squamous cell carcinoma (cSCC). cSCC generally appears on sun-exposed areas on white skin, such as:

  • the face
  • ears
  • lips
  • back of the hands
  • neck

In people of color, cSCC frequently develops in areas of the body not usually exposed to the sun, such as the legs, feet, buttocks, and groin region. In people of color, the carcinoma may begin under a nail as a dark streak and may also cause nail deformity.

cSCC may have the following signs:

  • a rough-feeling, scaly patch
  • an open sore
  • darker spots that a person may confuse for age spots
  • a growth that looks like a wart
  • a small growth on the skin that resembles a rhinoceros horn
  • a sore emerging in an old scar

These growths, or lumps, may grow over a period of weeks or months. cSCC does not look the same on every person, and the color can vary greatly depending on skin tone and other factors. cSCC may present as red or pink, brown, black, yellow, or white.

Some people may also experience symptoms such as:

  • itchiness
  • soreness or tenderness at the location of the cSCC
  • numbness or a pins-and-needles sensation

Most cSCCs result from frequent sun exposure. This is because UV light from the sun damages the DNA of the skin cells. The same damage to the skin cells’ DNA can result from UV light from tanning beds or lamps.

More than 90% of SCC cases result from DNA mutations. The mutations cause the squamous cells to grow at an abnormal and accelerated rate.

In immune-suppressed people, the human papillomavirus (HPV), or wart virus, may play a role in the development of SCC developing.

Certain risk factors can also increase the risk of a person developing SCC. These include:

  • frequent exposure to UV radiation without adequate protection
  • a weak immune system
  • a history of skin cancer
  • being over 50 years of age
  • having fair skin
  • being male
  • being exposed to certain chemicals such as arsenic
  • already having a sun-sensitive condition such as xeroderma pigmentosum
  • smoking
  • having skin precancers such as actinic keratosis
  • living with HPV

Most SCCs of the skin are curable if people receive treatment early on. But if SCC is left untreated and advances, it can be more difficult to treat and can lead to complications.

For example, the SCC can spread to the lymph nodes and travel to other tissues and organs (metastasis).

A person should see a doctor if they notice a growing spot, round lump, or scaly patch on their skin that feels different from the rest of their skin. The spot may bleed or change in another way.

A person should also see their doctor if they have an open sore that does not heal after a few weeks.

A doctor will usually begin by examining the area of the skin in question. They may ask questions, such as whether the lump or spot has changed in any way and if any risk factors of SCC are present.

The doctor may use a technique known as dermoscopy to observe the skin more closely using a type of magnifying lens known as a dermatoscope. They may then take a biopsy of the skin, which involves the removal of a small area of the skin. This sample is then sent to a laboratory for analysis under a microscope.

If the doctor suspects that the SCC has spread beyond the skin, they may request imaging tests, such as an MRI scan or a CT scan. Doctors may also send higher risk lesions off for additional testing.

Most cSCCs are curable when found early. There are several treatment options available for the removal of cSCC. Treatment options will depend on a variety of factors, including:

  • the size of the carcinoma
  • the location of the carcinoma
  • the type of carcinoma
  • whether the carcinoma has spread to the lymph nodes
  • whether the carcinoma has spread to other areas of the body

Surgery is a common treatment option for SCC. Surgical options include:

  • Excision: This involves cutting out the tumor, as well as a small border of unaffected skin.
  • Curettage and electrodesiccation: The doctor removes the tumor by scraping it and then destroying the remaining cancer cells with an electric needle.
  • Mohs surgery: This involves removing layers of skin and checking each layer for cancer cells until cancer cells are no longer seen in the skin sample. This form of surgery is the gold standard for lesions on the head and neck, hands, feet, genitals, and other high risk lesions.

Nonsurgical treatment options include:

  • Radiation therapy: This involves applying low energy X-rays onto the tumor.
  • Cryotherapy: This involves freezing and killing the cancer cells using liquid nitrogen.

Doctors may treat cSCC with topical immunostimulants or chemotherapeutic agents such as imiquimod or fluorocuracil, respectively.

Advanced SCCs may require different treatment options, such as removing the lymph nodes, immunotherapy, or more targeted chemotherapy.

The American Cancer Society recommends that a person checks their skin at least once a month. A person should do this in front of a full-length mirror and in a well-lit room.

Other recommendations for helping to prevent cSCC include:

According to the Skin Cancer Foundation, more than 15,000 Americans die every year from cSCC. cSCC is often treatable when detected early. For example, a 2017 study found that the 10-year survival rate for people with skin SCC after surgery was 93.6%.

A person’s outlook will depend on the staging of the carcinoma and whether it has spread to other areas. Other relevant factors include the person’s age, other conditions that may be present, and the characteristics of the tumor itself.

SCC is a common type of skin cancer. It begins in the squamous cells in a layer of the skin known as the epidermis. These cells become damaged and grow at an abnormal and accelerated rate.

Certain factors can increase the risk of a person developing cSCC, including their age, exposure to UV light, and having fair skin. Treatment options are available to remove cSCC.

Preventive measures can be taken to reduce the risk of developing cSCC, including reducing UV light exposure.