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. It begins in the epithelial tissue of the skin, or in the tissue that lines internal organs, such as the liver or kidneys. Carcinomas may spread to other parts of the body or be confined to the primary location. The disease has various forms.
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 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 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
This article will cover:
Carcinomas may occur in many parts of the body. Some common types of carcinoma include:
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.
While it’s impossible to know for sure who may develop cancer, certain factors may increase 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:
These factors may also raise the risk of cancer:
Other risk factors are specific to cancer type:
Exposure to UV rays is the main risk factor for both basal and squamous cell carcinoma. People with light-colored skin that easily burns or freckles are at greater risk than those who have darker skin, because they don’t have as much melanin, a skin pigmentation that serves as protection against the sun. Men are also more likely to get basal and squamous cell carcinoma. The risk increases with:
According to the American Cancer Society (ACS), men are two times as likely to develop renal cell carcinoma as women, and Black people have a greater chance than white people do of developing it. The over-the-counter pain reliever acetaminophen may be linked to increased risk. Additionally, the following conditions increase the risk of developing this type of cancer:
These types of breast cancer are most common in women who:
Carcinoma has been more commonly linked to these lifestyle factors and conditions:
The following causes are specific to cancer type:
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:
People with the following conditions are at increased risk of developing kidney cancer:
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.
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:
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.
The doctor may conduct a close visual examination of the patient’s skin called a dermoscopy, 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 these skin biopsies may also be collected:
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:
Testing to diagnose these types of breast cancer are often performed by a breast specialist or surgeon.
Tests include:
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. In general:
Doctors may simplify the above data using cancer stage grouping:
Treatment for carcinoma varies depending on the type, location and extent of the disease, but may include:
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.