Basal cell and squamous cell carcinomas

These skin cancers are among the most common types. They are typically caused when ultraviolet (UV) rays from the sun or tanning beds turn some normal skin cells into cancer cells.


Basal and squamous cell skin carcinomas start in the top layer of skin—the epidermis—and are often related to sun exposure.

The epidermis is made of three types of cells—basal cells, squamous cells and melanocytes. Skin cancer occurs when these cells grow out of control and invade the deeper layers of tissue below the epidermis.

Squamous cells are flat cells in the outer part of the epidermis, which are constantly shed as new ones form. Roughly two out of ten skin cancers are squamous cell carcinomas, also called squamous cell cancers. These cancers usually develop on sun-exposed areas of the body such as the face, ears, neck, lips and backs of the hands. Less often, they form in the skin of the genital area. Squamous cell cancers can usually be removed completely, although they are more likely than basal cell cancers to grow into deeper layers of skin and spread to other parts of the body.

Basal cells are in the lower part of the epidermis. About eight out of ten skin cancers are basal cell carcinomas, also called basal cell cancers, making it the most common type of skin cancer. These cancers usually develop on sun-exposed areas, especially the face, head and neck. Even though basal cell carcinoma grows slowly and rarely spreads, it can grow into nearby areas and invade the bone or other tissues beneath the skin if not treated.

Pre-cancerous and other skin conditions related to squamous cell carcinoma

Actinic keratosis (AK), also known as solar keratosis, is a pre-cancerous skin condition caused by too much exposure to the sun. AKs are small, rough or scaly spots that may be pink-red or flesh-colored. 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 them usually develop more than one.

Squamous cell carcinoma in situ, also called Bowen disease, is the earliest form of squamous cell skin cancer. The cells of these cancers are still only in the epidermis and have not invaded into deeper layers. Bowen disease appears as reddish patches. Like most other skin cancers and AKs, these patches most often appear in sun-exposed areas.

Bowen disease can also occur in the skin of the anal and genital areas, where it is known as erythroplasia of Queyrat or Bowenoid papulosis.

Keratoacanthomas are dome-shaped tumors that are found on sun-exposed skin. They may start out growing quickly, but their growth usually slows down, and many keratoacanthomas shrink or even go away on their own over time without any treatment.

Basal cell and squamous cell carcinomas causes

Genetic causes

While we understand the common risk factors for basal cell and squamous cell cancer, it’s still not completely clear how these factors cause cancer. We do know that most of these skin cancers are caused by repeated and unprotected exposure to UV rays from sunlight and tanning beds. UV rays can damage the DNA inside skin cells, the chemical that makes up our genes and that control how our cells function.

The gene most often altered in squamous cell cancers is the TP53 tumor suppressor gene. The gene often mutated in basal cell cancers are the PTCH1 or PTCH2 genes.

People with xeroderma pigmentosum (XP) have a high risk for skin cancer—XP is a rare, inherited condition resulting from a change in one of the XP (ERCC) genes.


Symptoms of basal cell carcinoma

  • Flat, firm, pale or yellow areas, similar to a scar.
  • Raised reddish patches that might be itchy.
  • Small, pink or red, translucent, shiny, pearly bumps, which might have blue, brown or black areas.
  • Pink growths with raised edges and a lower area in their center, which might contain abnormal blood vessels spreading out like the spokes of a wheel.
  • Open sores which may have oozing or crusted areas that don’t heal, or that heal and then come back.

Symptoms of squamous cell carcinoma

  • Rough or scaly red patches, which might crust or bleed.
  • Raised growths or lumps, sometimes with a lower area in the center.
  • Open sores which may have oozing or crusted areas that don’t heal, or that heal and then come back.
  • Wart-like growths.

Risk factors

  • UV light exposure. Believed to be the major risk factor for most skin cancer.
  • Having light-colored skin. Anyone can get skin cancer, but people with light-colored skin have a much higher risk than people with naturally darker skin color. This is because the skin pigment melanin has a protective effect in people with darker skin.
  • Being older. This is probably because of the buildup of sun exposure over time.
  • Being male.
  • Previous skin cancer.
  • Exposure to certain chemicals. Being exposed to large amounts of arsenic increases the risk of developing skin cancer.
  • Radiation exposure. People who have had radiation treatment have a higher risk of developing skin cancer in the area that received the treatment.
  • Xeroderma pigmentosum (XP). This very rare inherited condition reduces the ability of skin cells to repair DNA damage caused by sun exposure.
  • Long-term or severe skin inflammation or injury. Scars from severe burns, areas of skin over serious bone infections and skin damaged by some severe inflammatory skin diseases are more likely to develop skin cancers, although this risk is generally small.
  • Psoriasis treatment. Psoralens and ultraviolet light (PUVA) treatments given to some patients with psoriasis (a chronic inflammatory skin disease) can increase the risk of developing squamous cell skin cancer and probably other skin cancers.
  • Basal cell nevus syndrome, nevoid basal cell carcinoma syndrome or Gorlin syndrome. In this rare congenital condition, people develop many basal cell cancers over their lifetime. People with this syndrome may also have abnormalities of the jaw and other bones, eyes and nervous tissue.
  • Weakened immune system. People with weakened immune systems from certain diseases or medical treatments are more likely to develop many types of skin cancer. For example, people who get organ transplants are usually given medicines that weaken their immune system to help prevent their body from rejecting the new organ, which increases their risk of developing skin cancer.
  • Human papillomavirus (HPV) infection. Some HPV types, especially those that affect the genital and anal areas and the skin around the fingernails, seem to be related to skin cancers in these areas.
  • Smoking. Smokers are more likely to develop squamous cell skin cancer, especially on the lips. Smoking is not a known risk factor for basal cell cancer.

Source: American Cancer Society

Questions and answers (FAQs)

Why is squamous cell cancer so common?

Because it is caused by genetic mutations that occur from repeated exposure to the UV radiation from the sun. Most people leave some parts of their skin exposed to the sun on a regular basis.

Is squamous cell cancer curable?

Yes, when detected early and treated properly.

Can squamous cell carcinoma turn into melanoma?

No, they involve different types of cells.

How long does it take for basal cell carcinoma to spread?

This type of skin cancer spreads very slowly, and typically does not metastasize to other parts of the body. It can cause complications so proper treatment is necessary.


Because no two people develop skin cancer in the same way, we offer a wide array of resources for proper evaluation of your situation—and we use that information to create a personalized plan to fit your specific needs. Once a cancer has been diagnosed, our specialists need to know where it may have spread. This is the “stage” of the cancer. The lower the number, the less it has spread. Knowing the stage allows us to determine the best possible treatment plan for you.

We may use any combination of these tests and procedures to diagnose and stage skin cancer:

Biopsy. Removes all or part of the abnormal-looking skin growth for viewing under a microscope by an expert skin pathologist to check for signs of cancer.

CT scan (computed tomography). Uses a type of X-ray to create highly detailed and accurate cross-sectional images of the body.

Dermoscopy. Uses a drop of mineral oil on the lesion to reduce light reflection, make the skin more translucent, and to assist in viewing skin lesions to accurately distinguish between suspicious moles and other pigmented lesions.

Epiluminescence microscopy. Allows viewing of a lesion down to the dermo-epidermal junction—the areas where melanomas usually develop—that isn’t visible to the naked eye.

Excisional biopsy. Uses a scalpel to remove the entire growth.

Punch biopsy. Uses a special instrument called a punch to remove a circle of tissue from the abnormal-looking growth.

Skin examination. Uses a visual check of the skin for bumps or spots that look abnormal in color, size, shape or texture.


To stage basal and squamous cell skin cancer, UCHealth follows the American Joint Commission on Cancer (AJCC) TNM system.

The most recent version, effective as of 2018, applies only to squamous and basal cell skin cancers of the head and neck area (lip, ear, face, scalp and neck). The stage is based on 3 key pieces of information:

  1. The size of the tumor (T) and if it has grown deeper into nearby structures or tissues, such as a bone.
  2. If the cancer has spread to nearby lymph nodes (N).
  3. If the cancer has spread (metastasized) to distant parts of the body (M).

Numbers or letters after T, N, and M provide more details about each of these factors. Higher numbers mean the cancer is more advanced.

Once a person’s T, N and M categories have been determined, this information is combined in a process called stage grouping to assign an overall stage. The earliest stage of skin cancer is stage 0 (also called carcinoma in situ, or CIS). The other stages range from I (1) through IV (4). As a rule, the lower the number, the less the cancer has spread. A higher number, such as stage IV, means cancer has spread more.

If your skin cancer is in the head and neck area, talk to your doctor about your specific stage. Cancer staging can be complex, so ask your doctor to explain it to you in a way you understand.

Source: American Cancer Society


We find and treat most squamous cell and basal cell skin cancers at an early stage. We can remove or destroy them with local treatment methods, so we can usually cure them. Larger squamous cell cancers are harder to treat, and fast-growing cancers have a higher risk of coming back. Your medical team will work with you to create the best treatment plan for your unique case and recovery.

We may use any combination of surgery, chemotherapy, radiation or new immunotherapies to treat or control your cancer:

There are a few different types we can use:

  • Excision. Cutting out the tumor, along with a small margin of normal skin.
  • Curettage and electrodesiccation. Useful in treating small, thin squamous cell cancers.
  • Mohs surgery. Useful for squamous cell cancers that pose a higher risk for coming back, such as tumors larger than 2 cm (about 4/5 inch) across or with poorly defined edges, cancers that have come back after other treatments, cancers that are spreading along nerves under the skin and cancers on certain areas of the face or genital area.

Cryotherapy. Used for some early squamous cell cancers, especially in people who can’t have surgery.

Lymph node dissection. Might be recommended for some squamous cell cancers that are very large or have grown deeply into the skin, as well as if the lymph nodes feel enlarged and/or hard.

Radiation therapy or radiotherapy. X-rays and other types of medical radiation aimed at specific parts of the body. The radiation kills cancer cells, prevents cancer cells from developing or recurring, and improves many of cancer’s symptoms. For certain cancers, radiation therapy is combined with chemotherapy and called chemo-radiotherapy.

Systemic chemotherapy and/or targeted therapy. Chemotherapy and targeted therapy drugs (EGFR inhibitors) might be other options for patients with squamous cell cancer that has spread to lymph nodes or distant organs. These types of treatment might be combined or used separately.

Immunotherapy. Uses your own immune system to fight cancer.

Photodynamic therapy. Treatment that uses a certain type of laser light and a drug sensitive to that light to kill cancer cells. To treat skin cancer, laser light is shined onto the skin to activate the drug. Photodynamic therapy causes little damage to healthy tissue.


Skin Cancer Foundation. Basal Cell Carcinoma Overview (

American Cancer Society. Basal and Squamous Cell Skin Cancer (

National Center for Biotechnology Information (NCBI): National Library of Medicine. Squamous Cell Skin Cancer (

MedlinePlus: National Library of Medicine. Squamous cell skin cancer (