This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science

This page was updated on April 29, 2022.

Carcinoma is the most common type of cancer. Carcinomas may spread to other parts of the body or be confined to the primary location. The disease has various forms.

This article will cover:

What is carcinoma?

Carcinoma begins in the epithelial tissue of the skin, or in the tissue that lines internal organs, such as the liver or kidneys. It's the most common type of cancer, and has two subtypes: adenocarcinoma and squamous cell carcinoma.

While adenocarcinoma typically develops in the mucus membranes of glands or organs, squamous cell carcinoma develops in the cells that line body cavities and blood vessels, known as the squamous epithelium.

Metastatic carcinoma

When carcinoma has spread to other tissues and organs, it’s known as metastatic carcinoma. Although the terms are often confused, metastatic carcinoma is different from metastatic cancer, because not all cancers are carcinomas. 

Carcinoma in situ

Carcinoma in situ is an early-stage cancer that's confined to the layer of tissue from which it started and that hasn't spread to surrounding tissue or other parts of the body.

The care team may also use the term "in situ cancer" or "stage 0 cancer" to describe this early form of carcinoma.

Invasive carcinoma

Invasive carcinoma means the carcinoma has spread beyond the primary tissue layer to surrounding tissue. The care team may also use the term "infiltrating carcinoma" to describe this type of cancer.

Types of carcinoma

Carcinomas may occur in many parts of the body. Some common types of carcinoma include the following.

Basal cell carcinoma is the most common type of skin cancer. Cancerous cells develop in the basal cell layer of the skin, or the lowest part of the epidermis. Basal cell cancers usually grow slowly, and they rarely spread, or metastasize, to nearby lymph nodes or more distant parts of the body.

Squamous cell carcinoma is the second most common type of skin cancer. Cancerous cells develop from the flat, squamous cells that are the primary cell type making up the outermost layer of the skin, the epidermis. Squamous cell cancers usually grow slowly, and it is uncommon for them to spread, or metastasize. But they are more likely than basal cell carcinomas to invade fatty tissue beneath the skin or to spread even further.

Renal cell carcinoma is the most common type of kidney cancer. The cancerous cells typically develop in the lining of very small tubes in the kidney, called tubules. Over time, these cells may grow into a mass and cause an obstruction. The cancer may form in one or both kidneys.

Ductal carcinoma in situ is the most common type of breast cancer. Cancerous cells are confined to the lining of the milk ducts, and haven’t spread through the duct walls into surrounding breast tissue.

Invasive ductal carcinoma occurs when cancerous cells grow in the duct lining, break through the wall of the duct and invade local breast tissue. From there, the cancer may spread, or metastasize, to other parts of the body.

Carcinoma risk factors

While it’s impossible to know for sure who may develop cancer, certain factors may increase a person's carcinoma risk. For example, people with a family history of cancer or an inherited genetic mutation may be at greater risk.

Across all types of carcinoma, risk increases with:

  • Age
  • Alcohol use
  • Tobacco use
  • Exposure to ultraviolet (UV) radiation from the sun or tanning beds
  • Exposure to chemical or environmental irritants

These factors may also raise the risk of cancer:

Carcinoma causes

Carcinoma has been more commonly linked to these lifestyle factors and conditions:

  • Alcohol use
  • Tobacco use
  • Physical inactivity
  • Extra weight or obesity
  • Diet high in sugar and processed foods or red meat
  • Exposure to UV or other forms of radiation
  • History of certain viruses and infections

The causes listed below are specific to cancer type.

Basal and squamous cell carcinoma causes

UV radiation from the sun or tanning beds is the most common cause of these types of skin cancer.

People who have had certain types of HPV may also be at increased risk.

These genetic changes and conditions may increase the likelihood of developing basal or squamous carcinoma:

  • Altered TP53 tumor suppressor genes
  • Mutations to the PTCH1 or PTCH2 genes
  • The genetic condition xeroderma pigmentosum

Learn more about basal cell carcinoma risk factors and squamous cell carcinoma risk factors.

Renal cell carcinoma causes

People with the following conditions are at increased risk of developing kidney cancer:

  • Horseshoe kidneys (when kidneys are fused together at the bottom)
  • Von Hippel-Lindau disease
  • Adult polycystic kidney disease
  • Kidney failure

Additionally, the genes PRC, TFE 3 and VHL may be linked to renal cell carcinoma, but more research is underway to assess these and other genetic links.

Learn more about renal cell carcinoma risk factors.

Ductal carcinoma in situ and invasive ductal carcinoma causes

Changes to the DNA of breast cells may cause them to become cancerous. These mutations are inherited (passed down from relatives) or acquired (occurring during a person’s lifetime). Acquired changes to proto-oncogenes and tumor suppressor genes are the most common cause of breast carcinoma.

The following inherited gene mutations may lead to breast cancer:

  • BRCA1
  • BRCA2
  • PALB2
  • ATM
  • CHEK2

Learn more about ductal carcinoma in situ risk factors and invasive ductal carcinoma risk factors.

Carcinoma diagnosis

If a patient is experiencing symptoms, or the results of a screening test suggest cancer, the doctor will gather personal and family medical history and order more testing. A biopsy, or tissue sample, will likely be collected because it’s the only definitive way to diagnose cancer.

Tests for basal and squamous cell carcinoma

The doctor may conduct a close visual examination of the patient’s skin called a dermoscopy, This is a test in which a dermatoscope (a magnifying lens and light) is used to inspect the appearance (size, shape, color and texture) of any suspicious areas on the skin and to see whether there’s bleeding, crusting or oozing.

Because basal and squamous cell carcinomas may spread to the lymph nodes, doctors may check them for lumps.

Magnetic resonance imaging (MRI) or computed tomography (CT) scans of the area may be necessary.

One or more of the skin biopsies listed below may also be performed.

Shave biopsy: The skin’s top layers are shaved with a surgical blade.

Punch biopsy: A cookie-cutter-like tool is used to remove a small-but-deep skin sample so that all layers of the skin may be tested.

Excisional and incisional biopsies: A portion of the tumor (incisional) or the full tumor (excisional) is removed using a surgical knife.

Fine needle aspiration biopsy: Doctors may use a syringe to remove a small portion of a lymph node.

Surgical lymph node biopsy: The entire lymph node may be surgically removed if cancer is suspected.

Renal cell carcinoma diagnosis

If a patient is experiencing symptoms, or the doctor finds an abdominal mass during a physical examination, blood tests (such as a complete blood count and blood chemistry test) may be ordered to check on kidney function and other enzymes and cell counts.

Urine tests (urinalysis and urine cytology) to look for blood or cancer cells also may be performed. If a patient has renal cell cancer, there’s about a 50 percent chance blood will be present in the urine, according to the ACS.

Other testing may include those listed below.

CT scans are used along with a contrast dye that makes the area stand out. A CT scan helps determine the size, shape and location of a tumor, as well as whether or not it has spread. A CT-guided needle biopsy may also be done at this time.

MRI scans may be conducted if the patient is allergic to the contrast dye used in CT scans or has poor kidney function. MRI scans also provide a clear picture of blood vessels, which is helpful in finding out whether cancer has spread there.

Ultrasound images are helpful in locating a kidney mass, as well as determining whether the tumor is benign or malignant. A biopsy may also be taken using the ultrasound as a guide.

Angiography is a type of X-ray that examines blood vessels using a contrast dye to help map out blood vessels that may be feeding a tumor. This test may be performed to help plan for surgery.

Chest X-rays may be done to check for abnormal areas and see whether cancer has spread to the lungs.

Bone scans may be done if bone pain is present or blood tests indicate an increased calcium level. Low-level radioactive material is injected into the bloodstream, and a bone scan is performed to determine whether cancer has spread to the bones.

Kidney biopsy may be done if imaging alone does not provide enough information or diagnosis.

Ductal carcinoma in situ and invasive ductal carcinoma tests

Testing to diagnose these types of breast cancer is often performed by a breast specialist or surgeon.

Tests include those listed below.

Breast ultrasound: Pictures of the breast, acquired using sound waves, provide information about areas of concern.

Diagnostic mammogram: Any lumps or abnormal areas may be closely investigated using this tool, which provides a detailed X-ray of the breast.

MRI: This test may be done to take detailed images of areas inside of the breast.

Breast biopsy: A fluid or tissue sample may be taken for additional testing.

Carcinoma staging

The extent to which cancer has spread is called its stage. It’s important for doctors to determine the cancer stage in order to design the best course of treatment.

Cancer stage is determined during diagnosis and depends on the size, type and location of the cancer. Tumor grade is a term used to refer to the appearance and behavior of cancer cells (how likely they are to grow and spread).

TNM is the most common tumor staging system used to describe cancer, as explained in general terms below.

  • T (tumor): This represents the size and magnitude of the primary tumor and has the following subsets:
    • TX. The primary tumor is unmeasurable.
    • T0. A primary tumor isn’t detected.
    • T1, T2, T3, T4: These denote the size and progression of the primary tumor, increasing in progression with each number, and may be further broken down into subsets.
  • N (node): This represents the specific number of lymph nodes that also have cancer. and it has the following subsets:
    • NX. Presence of cancer in nearby lymph nodes is unmeasurable.
    • N0. Cancer isn’t detected in nearby lymph nodes.
    • N1, N2, N3. These denote the number and location where cancer-containing lymph nodes have been detected, increasing in progression with each number.
  • M (metastasis): This represents distant metastasis, or whether or not the cancer has spread to other areas, and it includes the following subsets:
    • MX. Rate of metastasis is unmeasurable.
    • M0. Cancer has not metastasized to other areas.
    • M1. Cancer has metastasized to other areas.

Doctors may simplify the above data using cancer stage grouping:

Stage 0 refers to cancer in situ, or cancer that’s limited to the place it started.

Stage 1 cancer hasn’t spread far into nearby tissues or other parts of the body.

Stage 2 is used to designate larger tumors and those that have spread deeply into nearby tissues and lymph nodes.

Stage 3 is similar to stage 2, but with increased severity.

Stage 4 is an advanced stage of metastatic carcinoma in which the primary cancer has spread to distant organs and areas of the body.

Carcinoma treatment

Treatment for carcinoma varies depending on the type, location and extent of the disease, but may include those listed below.

Surgery: Depending on the type of cancer, carcinoma may be treated with the surgical removal of cancerous tissue, as well as some surrounding tissue. Minimally invasive surgical treatment methods may help to reduce healing time and reduce the risk of infection after surgery.

Radiation therapy: Radiation therapy may be used in combination with surgery and/or chemotherapy. Advanced radiation therapies use image guidance before and during treatment on target tumors, and are designed to help spare healthy tissues and surrounding organs.

Chemotherapy: Chemotherapy treats carcinoma with drugs designed to destroy cancer cells, either throughout the whole body, or in a specific area. In some cases, chemotherapy may be used in combination with other treatments, such as radiation therapy or surgery.

Expert cancer care


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Show references
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  • American Cancer Society (2019, July 26). Basal and Squamous Cell Skin Cancer Risk Factors.
  • American Cancer Society (2020, February 1). Risk Factors for Kidney Cancer.
  • Centers for Disease Control and Prevention (2020, September 14). What Are the Risk Factors for Breast Cancer?
  • American Cancer Society. What Causes Cancer?
  • American Cancer Society (2020, June 9). Diet and Physical Activity: What’s the Cancer Connection?
  • American Cancer Society (2019, July 26). What Causes Basal and Squamous Cell Skin Cancers?
  • National Organization for Rare Disorders (2005). Renal Cell Carcinoma.
  • American Cancer Society (2019, September 18). How Does Breast Cancer Start?
  • National Cancer Institute (2019, July). How Cancer Is Diagnosed.
  • American Cancer Society (2019, July 17). Tests for Basal and Squamous Cell Skin Cancers.
  • American Cancer Society (2020, February 1). Tests for Kidney Cancer.
  • Centers for Disease Control and Prevention (2020, September 14). How Is Breast Cancer Diagnosed?
  • National Cancer Institute (2015, March 9). Cancer Staging.
  • American Society of Clinical Oncology (2018, March). Stages of Cancer.