Carcinoma is cancer that starts in the cells lining your organs and skin
Carcinoma is the most common type of cancer. It begins in the epithelial cells—the cells that form the outer layer of your skin and the inner lining of your organs like the lungs, stomach, breast, and colon. When these cells start growing abnormally and spreading, that growth is called carcinoma.
About 80 to 90 percent of all cancers are carcinomas. This high proportion exists simply because epithelial cells cover so much of your body's surface and line so many organs. The more cells of a certain type you have, the higher the statistical chance that one will develop a mutation that leads to cancer.
Carcinomas are named by where they start. Lung carcinoma starts in lung tissue. Breast carcinoma starts in breast tissue. Colon carcinoma starts in the colon. The location matters because it determines which organs are at risk, what symptoms you might notice first, and which treatments are most effective.
Key Takeaways
- Carcinoma develops in epithelial cells—the cells that line your skin and organs—making it the most common cancer type.
- Carcinomas are classified by their location, such as lung carcinoma, breast carcinoma, or colon carcinoma, which affects how they are treated.
- Two main subtypes exist: adenocarcinoma (starting in gland cells) and squamous cell carcinoma (starting in flat surface cells), each with different growth patterns.
- Risk factors vary by carcinoma type but often include smoking, sun exposure, family history, age, and certain infections.
How carcinoma develops from normal cells
Carcinoma does not appear overnight. It develops through a series of changes in epithelial cells over months or years. A single cell acquires a mutation—a change in its DNA—that causes it to divide when it should not. That cell divides into two identical copies, both carrying the same mutation. Those two divide into four, and so on.
Most of the time, your body's immune system catches these abnormal cells and destroys them before they become a problem. But occasionally a mutated cell escapes detection and keeps dividing. As it divides repeatedly, it may acquire additional mutations. Some of these new mutations make the cell more aggressive—better at dividing, better at avoiding immune detection, better at invading nearby tissue.
This process is called malignant transformation. It typically takes years. A person might have abnormal cells in their lungs for five years before those cells become lung carcinoma. This is why carcinoma risk increases with age: the longer you live, the more time mutations have to accumulate.
Adenocarcinoma and squamous cell carcinoma are the two main subtypes
Adenocarcinoma starts in gland cells—cells that produce mucus, sweat, or other secretions. These glands line your organs and skin. Adenocarcinomas are common in the lungs (even in people who have never smoked), the stomach, the colon, and the breast. They tend to grow more slowly than some other cancer types, but they can spread to distant organs.
Squamous cell carcinoma starts in flat, scale-like cells that form the outer layer of your skin and line your mouth, throat, and esophagus. These carcinomas are strongly linked to sun exposure (on the skin) and tobacco or alcohol use (in the mouth and throat). Squamous cell carcinomas of the skin are usually caught early because they appear on visible surfaces, but squamous cell carcinomas inside the body may not be noticed until they are more advanced.
A third, less common subtype is small cell carcinoma, which occurs almost exclusively in the lungs and grows very rapidly. There are also other subtypes specific to certain organs, but adenocarcinoma and squamous cell carcinoma account for the majority of cases across all carcinoma types.
Risk factors differ by carcinoma type but often overlap
Lung carcinoma risk is highest in current and former smokers, but also increases with radon exposure, asbestos exposure, and family history. Breast carcinoma risk rises with age, family history, certain genetic mutations (like BRCA1 and BRCA2), hormone use, and alcohol consumption. Colon carcinoma risk increases with age, inflammatory bowel disease, family history, and a diet high in red meat.
Skin carcinoma risk is driven primarily by sun exposure and skin type—people with fair skin burn more easily and have higher risk. Cervical carcinoma is strongly linked to infection with human papillomavirus (HPV). Stomach carcinoma risk is higher in people with a family history, those infected with Helicobacter pylori bacteria, and those who eat large amounts of salt-preserved foods.
Some risk factors you cannot change—age, family history, genetic mutations. Others you can influence—smoking, sun exposure, diet, alcohol use, and screening for infections. Knowing your personal risk factors helps you and your doctor decide whether screening tests make sense for you.
Carcinoma staging describes how far the cancer has spread
Once carcinoma is detected, doctors assign it a stage based on the size of the tumor and whether it has spread to nearby lymph nodes or distant organs. Staging uses the TNM system: T describes the size and depth of the tumor, N describes involvement of nearby lymph nodes, and M describes whether the cancer has spread to distant sites (metastasized).
Stage I carcinomas are small and confined to the organ where they started. Stage II carcinomas are larger or have spread to nearby lymph nodes. Stage III carcinomas have spread more extensively to lymph nodes or nearby tissue. Stage IV carcinomas have spread to distant organs—the lungs, liver, brain, or bones.
Stage matters because it predicts prognosis and guides treatment. A stage I breast carcinoma has a much higher five-year survival rate than a stage IV breast carcinoma. However, survival rates vary significantly by carcinoma type, subtype, and individual factors, so your doctor will discuss what the stage means for your specific situation.
Treatment depends on the type, stage, and location of the carcinoma
Surgery is often the first treatment for carcinoma that has not spread widely. A surgeon removes the tumor and a margin of surrounding tissue to reduce the chance that cancer cells remain. For some early-stage carcinomas, surgery alone may be curative.
Chemotherapy uses drugs to kill cancer cells throughout the body and is often used after surgery to destroy any cells that may have escaped, or before surgery to shrink a large tumor. Radiation therapy uses high-energy beams to kill cancer cells in a specific area. Targeted therapy and immunotherapy are newer approaches that work differently—targeted drugs attack specific mutations in cancer cells, while immunotherapy drugs help your immune system recognize and destroy cancer cells.
Many people receive a combination of treatments. Someone with stage III lung carcinoma might have chemotherapy and radiation, then surgery. Someone with stage II breast carcinoma might have surgery, then chemotherapy and radiation, then hormone therapy if the cancer is hormone-sensitive. Your treatment plan depends on what your doctors believe offers the best chance of controlling the cancer while managing side effects.
Frequently Asked Questions
Is carcinoma the same as cancer?
Carcinoma is a type of cancer, not all cancer. Cancer is a broad category that includes carcinoma, sarcoma (cancer of bone and muscle), lymphoma (cancer of immune cells), and leukemia (cancer of blood cells). Carcinoma is the most common category, accounting for about 80 to 90 percent of all cancers.
Can you survive carcinoma?
Survival depends on the type, stage, and subtype of carcinoma, as well as your age and overall health. Early-stage carcinomas often have high survival rates—for example, five-year survival for stage I breast carcinoma is around 99 percent. Advanced carcinomas have lower survival rates, but treatments continue to improve, and some people with stage IV carcinoma live for years with treatment.
What is the difference between carcinoma and melanoma?
Melanoma is a specific type of skin cancer that starts in melanocytes—the cells that produce skin pigment. Carcinoma of the skin (basal cell or squamous cell carcinoma) starts in different skin cells. Melanoma is less common but more aggressive than most skin carcinomas. Both are skin cancers, but they behave differently and are treated differently.
Does carcinoma always spread?
No. Early-stage carcinomas confined to one organ often do not spread, especially if treated with surgery. Some carcinomas grow slowly and may never spread. Others are more aggressive and spread to lymph nodes or distant organs. Whether a specific carcinoma spreads depends on its subtype, grade (how abnormal the cells look), and how quickly it is detected and treated.
Can you get carcinoma without risk factors?
Yes. While smoking increases lung carcinoma risk, some people who never smoke develop lung carcinoma. While sun exposure increases skin carcinoma risk, some people with minimal sun exposure develop skin carcinoma. Risk factors increase the probability, but they do not determine whether you will develop carcinoma. Random mutations can occur in anyone.