Carcinoma is the name given to a group of cancers that start in epithelial cells. These cells make up the tissue that lines the surfaces inside and outside your body.

This tissue, called the epithelium, is found on the outside surfaces of your skin and internal organs. It also includes the insides of hollow organs, like your digestive tract and blood vessels.

Carcinoma is the most commonly diagnosed type of cancer. It’s classified into subtypes based on the location and type of the epithelial cell it starts from.

Different types of carcinoma can develop in the same organ, so it’s sometimes better to categorize cancer by subtype instead of organ.

The most common carcinomas by subtype are:

Squamous cell carcinoma (SCC)

Squamous cell carcinoma develops in cells in the top layer of the epithelium, called squamous cells. Most often, squamous cell carcinoma refers to skin cancer, but it also commonly affects other parts of the body. It can affect the:

  • Skin (cutaneous SCC). This type grows slowly and doesn’t usually spread, but local invasion and metastasis occur more often than with basal cell carcinoma.
  • Lung. SSC represents up to 30 percent of all lung cancers.
  • Esophagus. Most cancers in the upper esophagus are SCC.
  • Head and neck. Over 90 percent of cancers in the mouth, nose, and throat are SCC.

Basal cell carcinoma

Basal cell carcinoma develops in cells in the deepest layer of the epithelium, called basal cells. It is the most common form of carcinoma and the only one that occurs exclusively in the skin.

According to the American Society of Clinical Oncology, about 80 percent of all skin cancers that aren’t melanoma are basal cell carcinomas.

Basal cell carcinoma is slow growing, almost never spreads, and is almost always caused by exposure to the sun.

Renal cell carcinoma (kidney cancer)

Renal cell carcinoma develops in the epithelial cells of the filtering system of the kidney. This type of cancer accounts for about 90 percent of all cancers in the kidney.

Transitional cell carcinoma

Transitional cell carcinoma develops in the stretchy cells in the urinary tract epithelium, called transitional cells. Transitional cells are found in the center of your kidney (renal pelvis) and in the tube (ureter) that drains urine from your kidney.

Transitional cell carcinoma accounts for less than 10 percent of all kidney tumors.


Adenocarcinoma is a family of cancers that start in specialized epithelial cells, called glandular cells. Glandular cells are found in the linings of most organs and secrete a substance like mucus.

The most common adenocarcinomas are:

The general risk factors for carcinoma are similar to the risk factors for all other cancers. These risk factors include:

  • age
  • poor dietary habits
  • misuse of substances such as alcohol and tobacco
  • genetics
  • exposure to certain chemicals

For squamous cell and basal cell carcinomas, both forms of skin cancer, exposure to UV radiation (including tanning beds) is a significant risk factor.

A doctor who suspects that you may have a form of carcinoma will begin by taking your medical history and performing a physical examination to evaluate your symptoms and areas of concern.

If you have a skin lesion, your doctor will be able to tell if it’s likely to be a basal or squamous cell carcinoma based on its characteristics, such as its:

  • size
  • color
  • shape
  • texture
  • growth rate

Of carcinomas that appear on the skin, basal cell carcinomas are more likely to be small and have a pearly sheen, while squamous cell carcinomas vary in shape and appearance and are more likely to be mistaken for sores or warts.

Carcinoma inside your body is evaluated with imaging tests that allow doctors to spot a tumor’s location and size. The tests can also show if the tumor has spread locally or within your body.

These imaging tests include:

Once the cancer has been evaluated with imaging, a biopsy is performed. A part or all of the lesion is surgically removed and looked at under a microscope to determine if it’s cancer and what kind it is.

Depending on how raised a lesion is and how deep your doctor suspects the affected tissue to be, a biopsy of the skin can involve scraping off a few layers of tissue or using a tool called a punch to take a larger sample. For biopsies taken from a location inside the body, your doctor may require you to go under anesthesia.

Special scopes — which are lighted tubes with a camera and special tools designed for a specific organ — are often used to look at the cancer and tissue around it, and biopsy or remove the cancer.

Categorizing carcinomas

Once a carcinoma is diagnosed, it’s categorized as one of three types, depending on if and how it spreads. These types include:

  • Carcinoma in situ. This means the cancer hasn’t spread outside of the epithelial cells it started in.
  • Invasive carcinoma. This means the cancer has spread locally into neighboring tissue.
  • Metastatic carcinoma. This means the cancer has spread to distant parts of the body that are not near the epithelium.

A carcinoma will be treated with a combination of surgery, radiation therapy, and chemotherapy depending on:

  • the cancer’s location
  • how advanced it is
  • whether it has spread locally or to a distant part of the body

Treatments are typically used in the following ways:

  • Surgery is used to remove all of the cancer or as much of it as possible.
  • Radiation therapy is usually used to treat a specific area with local cancer spread.
  • Chemotherapy is usually used to treat cancer that may have spread distantly.

The outlook for any carcinoma depends on:

  • how advanced it is when it’s diagnosed
  • if it has spread locally or to other organs
  • how early treatment is started

Carcinoma that’s caught early before it has spread is more likely to be fully removable or easily treatable, with less risk of reappearing in the future.

As a group, carcinomas are the most common type of cancers. Even within each subtype of carcinoma, the severity of the disease and the available treatment options can vary widely from case to case.

Most carcinomas can potentially become life threatening if not treated promptly, but a carcinoma that’s found and treated early may be cured in many cases.

If you are facing a more serious diagnosis with longer treatment time, social support from friends, family, and local and online communities can help ease some of the difficulties of recovery. The American Cancer Society offers a number of helpful resources, including support groups and rides to treatment.

Information and support

If you or a loved one could benefit from support while being treated for carcinoma, check out the following resources.