What is a tumor?

What is a tumor?

A tumor is a tissue mass or lump that may cause swelling. Not all tumors are cancerous but if one occurs, it’s a good idea to see a doctor.

The National Cancer Institute defines a tumor as “an abnormal tissue mass that results when cells divide more than they should or do not die when they should.” Cells grow, divide, and replace one another in the body in a healthy body. The old ones die as new cells form. New cells develop when a person has cancer when the body doesn’t need them. A group of cells or tumor can grow if there are too many new cells.

With certain tumors being benign and composed of noncancerous cells, some are malignant. Malignant tumors are cancerous, and can spread the cells to other areas of the body.

What is a tumor?

If the cells multiply too rapidly a tumor grows.

Depending on the form, tumors can range in size from a tiny nodule to a massive mass and they can appear almost anywhere on the body.


Fibroids are a type of benign tumor
Fibroids are a type of benign tumor. Photo credit: Dodoïste, 2012

There are three main types of tumor:

Benign: These are not cancerous. They either cannot spread or grow, or they do so very slowly. If a doctor removes them, they do not generally return.

Premalignant: In these tumors, the cells are not yet cancerous, but they have the potential to become malignant.

Malignant: Malignant tumors are cancerous. The cells can grow and spread to other parts of the body.

How a tumor will function in the future isn’t always obvious. Some benign tumors can become premalignant, and malignant afterwards. It is for that reason that tracking some development is best.


Most benign tumors are not dangerous, and certain areas of the body are unlikely to get affected.

But, if they push against nerves or blood vessels or if they activate overproduction of hormones, as in the endocrine system, they may cause pain or other problems.

Benign tumor types include:


Adenomas develop in the glandular epithelial tissue that is the thin membrane covering the body’s glands, organs, and other structures.

Examples include:

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

Adenomas do not start as cancer. Some, however, can change, and become cancerous adenocarcinomas.


Fibroids, or fibromas, are benign tumors which can develop on any organ’s fibrous or connective tissue.

Uterine fibroids are common and can cause:

  • vaginal bleeding
  • pelvic pain or discomfort
  • urinary incontinence

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

There are many types of fibroma, including:

Many fibromes may cause symptoms, and may need to be monitored. Fibroids can alter in rare cases, and become fibrosarcomas. Those are carcinogenic.


Hemangiomas are benign tumors that develop excessively as blood vessels expand.

They may appear on the skin as red “strawberry lines,” or may grow within the body. We are always present at birth and in infancy, we vanish.

Hemangiomas typically do not require care but if they do not go down, laser therapy and other treatments are available.


Lipomas are most common in people from 40–60 years old.

Lipomas are a tumor shaped by soft tissue and composed of fat cells. According to the American Academy of Orthopedic Surgeons (AAOS), they can occur at any age but mostly affect people ages 40–60.

Most lipomas are small, painless, rubbery, mobile and soft to the touch. They also appear on the back, elbows, neck, buttocks, and leg tops.

The AAOS says they’re unlikely to become cancerous.

Lipoma forms include fibrolipomas that include fat cells and fibrous connective tissue, and angiolipomas that occur below the skin.


This type of tumor is not cancerous, but it needs close monitoring in case it changes.

Examples include:

Actinic keratosis

This development also known as solar keratosis includes patches of crusty, scaly, and dense skin.

Fair-skinned people are more likely to get hurt, and sun exposure increases the risk.

Actinic keratosis sometimes transforms into squamous cell carcinoma, so doctors usually recommend treatment of it.

Cervical dysplasia

During cervical dysplasia, the cells that line the cervix are subject to a transition. Those cells may be found by a doctor during a Pap smear. Cervical dysplasia is often the result of the human papillomavirus (HPV), an infection widespread among young people.

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

The cells may be separated by a surgeon using freezing methods or by removing a tissue cone from the cervix.

Metaplasia of the lung

These growths take place in the bronchi, the tubes which carry air into the lungs.

Bronchial lining includes glandular cells. This can shift and become squamous cells, or cancer, in some people like smokers.


Leukoplakia causes thick white patches to form in the mouth.

These patches:

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

If someone with this form of patch does not go away within 2 weeks, they should see a doctor.

They will also track changes to the patches and, where appropriate, quit smoking or chewing tobacco.

If a doctor thinks the patches could become cancerous, he or she may use a laser or surgical scalpel to remove it.


There are cancerous malignant tumours. When cells grow uncontrollably they develop. If the cells keep growing and spreading, the disease may become life-threatening.

In a process called metastasis malignant tumors may develop rapidly and spread to other parts of the body.

The cancer cells migrate to other areas of the body are the same as the initial ones, but they are capable of entering other organs. For example, if lung cancer spreads to the liver, the cancer cells in the liver also form lung cancer cells.

Numerous types of malignant tumors arise from various cell types.

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: These tumors 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 they 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.


MRI to diagnose a tumor
A doctor may suggest an MRI to diagnose a tumor.

Often a person can see or feel a tumor, but some may only show up on imaging tests, including a mammogram or an MRI. However, such tests can only detect the presence of a lump.

A biopsy is required to determine lump form. The doctor shall take a small sample of tissue and send it to a laboratory where it will be examined under a microscope by technicians.

The doctor can take the sample in his office, using a needle, or to extract the tumor during a surgical procedure.

They can first determine that a person needs surgery if they believe that a tumor is malignant, or if it presses on a nerve or causes other issues.


The outlook for a tumor-stricken person will depend on their condition.

Many benign tumors do not face major health hazards. However, doctors can recommend that they should be removed only in case.

A malignant tumor may be more challenging to treat but it is usually possible to treat it effectively in the early stages. It is crucial for people to undergo regular health checks for this reason, because this can also make early detection possible.

Someone who notices a lump on their body, development, or any odd change should see a doctor. Growth will not usually be a cause for concern, but it’s better to check.


Do all cancers involve a tumor?


Yes, all cancers involve some form of solid or liquid tumor. In general, a tumor is a swollen mass of tissue that arises from the uncontrolled division of cells.

In addition to being either malignant or benign, tumors can be either solid or liquid. Solid tumors get their names, such as sarcomas, carcinomas, and lymphomas, from the type of cell that forms them. In solid tumors, the mass of tissue does not include liquid areas or cysts. Some types of cancer, for example, leukemia, which is cancer of the blood, do not form solid tumors. Christina Chun, MPH

Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.


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