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

This includes the outside surface of your skin and internal organs. It also includes the inside of hollow organs, like your digestive tract and blood vessels.

Carcinoma is the most commonly diagnosed type of cancer. It’s classified into subtypes by the kind of cell it starts from.

Most common subtypes of carcinoma

  • Basal cell carcinoma. This type develops in cells in the deepest layer of the epithelium, called basal cells.
  • Squamous cell carcinoma. This type develops in cells in the top layer of the epithelium, called squamous cells.
  • Transitional cell carcinoma. This type develops in the stretchy cells in urinary tract epithelium, called transitional cells.
  • Renal cell carcinoma. This type develops in the epithelial cells of the filtering system of the kidney.
  • Adenocarcinoma. This type starts in specialized epithelial cells, called glandular cells.

Sarcoma is another type of cancer. It’s different from carcinoma because, rather than the epithelium, it starts in cells in connective tissue, which is found in bone, cartilage, tendons, and muscle.

Sarcomas occur much less frequently than carcinomas.

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:

Basal cell carcinoma

This only occurs 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.

It’s slow growing, almost never spreads, and is almost always caused by exposure to the sun.

Squamous cell carcinoma (SCC)

Most often, squamous cell carcinoma refers to skin cancer, but it also commonly affects other parts of the body:

  • Skin (cutaneous SCC). This grows slowly and doesn’t usually spread, but local invasion and metastasis occur more often than with basal cell carcinoma.
  • Lung. According to the American Cancer Society, SSC represents about 25 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.

Renal cell carcinoma (kidney cancer)

This type of cancer accounts for about 90 percent of all kidney tumors.

Transitional cell carcinoma

Transitional cells are found in the center of your kidney (renal pelvis) and the tube that drains urine from your kidney (ureter).

Transitional cell carcinoma accounts for about 10 percent of all kidney cancers.

Adenocarcinomas

These cancers develop in epithelial cells that secrete a substance like mucus, called glandular cells. These cells are in the linings of most organs.

The most common adenocarcinomas are:

Categorizing carcinomas

Once any of these carcinomas is diagnosed, it’s categorized as one of three types depending on if and how it spreads:

  • 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 not near the epithelium

A history and physical is performed to see if your symptoms are consistent with carcinoma and to look for any signs of it on examination.

Skin lesions that might be cancer are looked at by your doctor who can tell if it’s likely to be a basal or squamous cell carcinoma based on its characteristics, such as:

  • size
  • color
  • shape
  • texture
  • growth rate

Carcinoma inside your body is evaluated with imaging tests that show its location and size. They can also show if it has spread locally or within your body.

These 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.

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.

All carcinomas are treated with a combination of surgery, radiation therapy, and chemotherapy depending on its location, how advanced it is, and whether it’s spread locally or to a distant part of the body.

  • 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’s spread locally or to other organs
  • how early treatment is started

Carcinoma that’s caught early before it has spread can be cured, giving a good outcome. The longer the time before treatment or the more the carcinoma has spread, and the more difficult the outcome may be.

A system of support made up of family, friends, and local and online communities is needed by anyone who’s diagnosed with carcinoma.

A good resource for finding these types of support is the Cancer.Net website created by the ASCO.

Information and support

Carcinoma is the most common kind of cancer and can occur in almost any part of your body. Most can potentially become life-threatening if not treated promptly.

A carcinoma that’s found and treated early may be cured in many cases.