What Is a Tumor?

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A tumor—also referred to as a "neoplasm"—is an abnormal mass of tissue formed when cells grow and divide at rates that are faster than usual, or when cells don't die when they should. Some tumors are benign, meaning that they are not an indication of cancer and don't spread into surrounding parts of the body. Other tumors, though, are cancerous—or malignant—and do invade other areas of the body via the bloodstream and lymphatic systems.

doctor looking at mammogram

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Causes of Tumors

Typically, cells divide and grow at a particular rate in order to replace older cells, or to allow them to perform new functions. But human bodies don't always follow that pattern, sometimes experiencing uncontrolled cell growth, and/or damaged or older cells that don't die in order to make room for their replacements.

When that cell life cycle gets out of whack, it's possible for a tumor to form as a result—especially if a person's immune system isn't functioning properly. On top of that, there are additional factors that can increase a person's risk of getting cancer (which typically involves a tumor), including:

  • Genetic problems
  • Drinking too much alcohol
  • Viruses
  • Environmental toxins, such as certain poisonous mushrooms and a type of poison that can grow on peanut plants (aflatoxins)
  • Excessive sunlight exposure
  • Obesity
  • Radiation exposure
  • Benzene and other chemicals and toxins.

In some cases, it's not unusual to see one type of tumor in one sex over the other, or in children or older adults.

While viruses are not responsible for all tumors, the following are examples of tumors either caused by or linked to viruses:

  • Cervical cancer (human papillomavirus)
  • Most anal cancers (human papillomavirus)
  • Some throat cancers, including soft palate, base of tongue and tonsils (human papillomavirus)
  • Some vaginal, vulvar, and penile cancers (human papillomavirus)
  • Some liver cancers (hepatitis B and hepatitis C viruses)
  • Kaposi sarcoma (human herpesvirus 8)
  • Adult T-cell leukemia/lymphoma (human T-lymphotropic virus-1)
  • Merkel cell carcinoma (Merkel cell polyomavirus)

Types of Tumors

Whether you first spot a tumor yourself, or your healthcare provider finds one during an exam or routine screening, it can be unsettling. But it's important to keep in mind that not all tumors are a sign of cancer. While some—known as malignant tumors—are, others are benign, and though they may grow to be quite large, are not cancerous.

Also, a practitioner may find what's called a "premalignant tumor," which has the potential to become cancer and therefore is important to keep an eye on.

Benign Tumors

Benign tumors tend to stay in one spot on a person's body, instead of invading neighboring regions. In fact, they typically grow slowly and have distinct borders.

While not typically a sign of cancer, some benign tumors have the potential to eventually turn into malignant tumors and require close monitoring by the patient and their healthcare provider. In those cases—as well as those where the tumor may cause other medical problems for a person—surgical removal may be necessary or recommended.

Malignant Tumors

Unlike benign tumors, malignant tumors invade other parts of the body and are capable of spreading both to nearby and far away regions.

They are able to reach distant sites on the body through the bloodstream or the lymphatic system, in a spread known as "metastasis." Though metastasis can happen anywhere, it's most common in the liver, lungs, brain, and bone. Given how quickly malignant tumors can spread, they require treatment in order to stop their growth.

Symptoms of Tumors

Because tumors can be found anywhere in the body, their symptoms can depend on where they're located. For instance, lung tumors may cause coughing, shortness of breath, and/or chest pain, while tumors of the colon may involve weight loss, diarrhea, constipation, iron deficiency anemia, and/or blood in the stool. Here are some of the most common symptoms associated with tumors:

  • Fever or chills
  • Fatigue
  • Loss of appetite
  • Night sweats
  • Weight loss
  • Pain

Additionally, not all tumors come with symptoms, and some, like the ones caused by pancreatic cancer, typically don't show up until a person has reached an advanced stage of the disease.

Diagnosing Tumors

While some tumors are visible externally, most are located inside the body and are spotted during routine screenings like mammograms, colonoscopies, or prostate exams. But regardless of how a tumor is found, the next step is to conduct a biopsy—when a small piece of a tumor is removed and then examined under a microscope to determine whether or not it's cancerous. Other tests include:

  • Blood tests
  • Bone marrow biopsy (most often for lymphoma or leukemia)
  • Chest X-ray
  • Complete blood count (CBC)
  • Liver function tests

To get a better picture of the tumor and determine if or where it has spread, healthcare providers may order a computerized tomography (CT) scan, positron emission tomography (PET) scan, or magnetic resonance imaging (MRI). 

Treatment of Tumors

How a tumor is treated not only depends on whether it is benign or malignant, but also the risks and benefits of various procedures in relation to its location. Here's what to know about each type.

Benign Tumors

For the most part, benign tumors themselves aren't major threats to a person's health, but that doesn't mean that they're not annoying, painful, or could be the source of other medical complications.

For instance, if a person had a large benign tumor on their lung, it could compress their windpipe and make it harder for them to breathe, meaning that surgical removal may be necessary or at least recommended for a better quality of life.

The same case could be made for other benign tumors like lipomas in the skin, or fibroids in the uterus—both of which are often removed.

Malignant Tumors

The treatments for a malignant tumor depends on how soon it is identified and how much it has spread, and include one, or a combination of the following:

  • Chemotherapy
  • Radiation
  • Surgery
  • Targeted cancer therapy
  • Immunotherapy
  • Other treatment options

A Word From Verywell

Most tumors are not large, visible masses, which is yet another reason why routine cancer and blood screenings are so important. It's also important to keep in mind that there are many different types of tumors and cancers.

Getting any news that might suggest that cancer is a possibility can be deeply upsetting, but no two cases are exactly alike. If you find yourself in that position, be your own advocate—not only standing up for yourself when necessary but also asking all the questions you need in order to feel informed about your diagnosis.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Cancer Institute. Cancer terms: tumor.

  2. MedlinePlus. Tumor.

  3. Patel A. Benign vs malignant tumorsJAMA Oncol. 2020;6(9):1488. doi:10.1001/jamaoncol.2020.2592

By Elizabeth Yuko, PhD
Elizabeth Yuko, PhD, is a bioethicist and journalist, as well as an adjunct professor of ethics at Dublin City University. She has written for publications including The New York Times, The Washington Post, The Atlantic, Rolling Stone, and more.