There are three main types of tumor; benign, premalignant, and malignant. If someone has a malignant tumor, it is cancerous. Other types of tumor are not cancerous.

This article discusses the different types of tumors, their causes, treatments, and outlooks.

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A tumor develops when cells reproduce too quickly.

The National Cancer Institute defines a tumor as “an abnormal mass of tissue that results when cells divide more than they should or do not die when they should.”

Tumors can vary in size from a tiny nodule to a large mass, depending on the type, and they can appear almost anywhere in the body.

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There are three main types of tumor:

  • Benign: These tumors are not cancerous. They do not invade nearby tissue or spread to other parts of the body. If a doctor removes them, they do not generally return.
  • Premalignant: In these tumors, the cells are not yet cancerous, but they can potentially become malignant.
  • Malignant: Malignant tumors are cancerous. The cells can grow and spread to other parts of the body.

It is not always clear how a tumor will act in the future. Some benign tumors can become premalignant and then malignant. For this reason, it is best to monitor any growth.

Tumor vs. cyst

Tumors and cysts can look similar, and both can form on almost any part of the body.

However, tumors are solid tissue masses, while cysts are sacs containing other substances, such as fluid or air. Due to their content, cysts may appear softer to the touch than tumors, which typically feel firm. However, some benign tumors can also feel soft to the touch.

Learn more about the differences between tumors and cysts here.

Most benign tumors are not harmful, and are unlikely to affect other parts of the body.

However, they can cause pain or other problems if they press against nerves or blood vessels or trigger the overproduction of hormones, as in the endocrine system.

Examples of benign tumors include:


Adenomas develop in glandular epithelial tissue, which is the thin membrane that covers glands, organs, and other structures in the body.

Examples include:

  • colon polyps
  • fibroadenomas, a common form of benign breast tumor
  • hepatic adenomas, which occur in the liver

Adenomas do not start as cancer. However, some can change and become adenocarcinomas, which are cancerous.

Learn more about fibroadenomas of the breast here.


Fibroids, or fibromas, are benign tumors that can grow on the fibrous or connective tissue of any organ.

Uterine fibroids are common and can cause:

They can be “soft” or “hard,” depending on the proportion of fibers to cells.

There are many types of fibroma, including angiofibromas, which can appear as small red bumps on the face, and dermatofibromas, which appear on the skin, often on the lower legs.

Some fibromas can cause symptoms and may need surgery. In rare cases, fibroids can change and become fibrosarcomas. These are cancerous.

Learn more about dermatofibromas.


Hemangiomas are benign tumors that form when blood vessels grow excessively.

They can appear as discolored marks on the skin or develop inside the body. They are often present at birth and disappear during childhood.

Hemangiomas do not usually need treatment, but laser surgery and other options are available if they do not go away.

Find out more here about internal hemangiomas.


Lipomas are a form of soft tissue tumor and consist of fat cells. They can appear at any age but often affect people from 40–60 years old and are unlikely to become cancerous.

Most lipomas are small, painless, rubbery, soft to the touch, and movable. They often appear on the back, shoulders, arms, buttocks, and the tops of the legs.

Types of lipoma include fibrolipomas, which contain fat cells and fibrous connective tissue, and angiolipomas, which appear under the skin.

Find out more about angiolipomas here.

This type of tumor is not cancerous, but doctors will monitor them closely for changes.

Examples include:

Actinic keratosis

Also known as solar keratosis, this growth involves crusty, scaly, and thick skin patches.

It is more likely to affect fair-skinned people, and sun exposure increases the risk.

Sometimes, actinic keratosis will transform into squamous cell carcinoma, so doctors usually recommend treating it.

Cervical dysplasia

In cervical dysplasia, a change occurs in the cells that line the cervix. A doctor may find these cells during a Pap smear. Cervical dysplasia often stems from the human papillomavirus (HPV), an infection common in young people.

The cells are not cancerous, but they may become malignant 10–30 years later, resulting in cervical cancer.

A surgeon may remove the cells using freezing techniques or taking a cone of tissue from the cervix.

Metaplasia of the lung

These growths occur in the bronchi, the tubes that carry air into the lungs.

The lining of the bronchi contains glandular cells. In some people, including smokers, these can change and become squamous cells or cancer.


Leukoplakia causes thick white patches to form in the mouth.

These patches:

  • are painless
  • have an irregular shape
  • have raised edges
  • are not possible to scrape off

Anyone with this type of patch should see a doctor if it does not go away with time.

They should also monitor the patches for changes and quit smoking or chewing tobacco.

If a doctor believes the patches could become cancerous, they may use a laser or surgical scalpel to remove them.

Learn more about leukoplakia here.

Malignant tumors are cancerous. They develop when cells grow uncontrollably. If the cells continue to grow and spread, the disease can become life threatening.

Malignant tumors can grow quickly and spread to other parts of the body in a process called metastasis. However, not all malignant tumors grow quickly; some can grow much slower over time.

The cancer cells that move to other parts of the body are the same as the original ones, but they can invade other organs. For example, if lung cancer spreads to the liver, the cancer cells in the liver are still lung cancer cells.

Different types of malignant tumors originate in different types of cells.

Examples include:

  • Carcinoma: These tumors form from epithelial cells, which are present in the skin and the tissue that covers or lines the body’s organs. Carcinomas can occur in the stomach, prostate, pancreas, lung, liver, colon, or breast. They are a common type of malignant tumor.
  • Sarcoma: Sarcomas start in connective tissue, such as cartilage, bones, fat, and nerves. They originate in the cells outside the bone marrow. Most sarcomas are malignant.
  • Germ cell tumor: These tumors develop in the cells that produce sperm and eggs. They usually occur in the ovaries or testicles but may also appear in the brain, abdomen, or chest.
  • Blastoma: These tumors form from embryonic tissue or developing cells. Blastomas are much more common in children than in adults. They can lead to tumors in the brain, eye, or nervous system.
  • Meningiomas: These are among the most common types of brain tumors and sometimes require excision or treatment if they are causing symptoms.

Testicular cancer starts in the germ cells. Learn more here.

Tumors result from an overgrowth of cells.

In a healthy body, cells grow, divide, and replace each other in the body. As new cells form, the old ones die. If too many new cells exist, a group of cells, or tumor, can develop.

For example, when a person has cancer, new cells form when the body does not need them.

Benign tumors may develop due to:

  • injury
  • environmental toxins
  • infection

Risk factors

While the exact causes of tumor growth are often unclear, several factors can increase a person’s risk.

Risk factors for malignant tumors include:

The risk level of the above can vary across different people and different types of cancer.

Risk factors for benign tumors include:

  • frequent exposure to toxins and radiation
  • stress
  • diet
  • family history of tumors
  • frequent infections

A person can sometimes see or feel a tumor, but others will only show up on imaging tests, such as mammograms or MRIs. Screening tests such as colonoscopies and Pap smears can also pick up malignant and pre-cancerous tumors.

A biopsy may be necessary to determine the type of lump. The doctor will take a small tissue sample and send it to a laboratory where technicians will examine it under a microscope.

The doctor may take the sample either in their office, using a needle, or during a surgical procedure to remove the tumor.

They may decide that a person needs surgery first if they suspect that a tumor is malignant or if it is pressing on a nerve or causing other problems.

Learn more about what a biopsy involves.

The outlook for a person with a tumor will depend on its type.

Many benign tumors pose no significant health risks. However, doctors may recommend removing them just in case.

A malignant tumor can be more challenging to treat, but effective treatment is usually possible in the early stages. For this reason, people need to attend routine health checks, as these can often make early diagnosis possible.

Anyone who finds a lump, growth, or another unusual change in their body should see a doctor. Usually, the growth will be no cause for concern, but it is better to check.

Tumors are overgrowths of tissue and occur due to abnormal cell growth. Tumors can occur almost anywhere in the body.

There are three main types of tumor; benign premalignant, and malignant. Benign and premalignant tumors can be harmless, whereas malignant tumors are cancerous.

A person’s outlook and treatment options will depend on their type of tumor. Early detection and diagnosis of all tumors are essential to proper management.