Distinguishing Breast Cancer Tumors From Benign Masses

Several factors can help differentiate the two

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Breast changes over the course of a woman's life are common. Your genes and stage of life, from puberty to menopause, can all affect how your breasts develop, look, and feel.

Sometimes breast lumps develop that are benign (noncancerous). Only 3% to 6% of breast lumps are due to breast cancer. Self-exams each month may be helpful in identifying the lumps, but an exam done by a healthcare provider is needed to find out for sure what's going on in your breast.

This article will help explain the differences between noncancerous and cancerous tumors. It will help you to better understand how they are diagnosed and what to do about them.

breast cancer imagery
Verywell / Jessica Olah
  Cancerous Noncancerous
Feel Firm, irregular margins, immobile Squishy, defined margins, mobile
Mammogram Spiky, fuzzy, or lumpy Uniform, round, or oval
MRI Rapidly lights up and fades Slow to light up, doesn't fade
Biopsy Cell clusters, irregular nuclei Same as normal cells

How a Cancerous Tumor Differs From a Benign Mass

A breast specialist can learn much by how a breast mass feels. It can help them to determine whether a lump is a breast cancer tumor or a benign mass.

Signs of Cancerous Masses

Cancerous masses in the breast are often very firm, like a rock. They have an irregular shape and size. They can be mobile but are often fixed, meaning they feel like they are attached to the skin or nearby tissue. You can't really move them around by pushing on them. They're also not likely to be painful, though they can be in some cases.

On exam, other changes may be present as well. These changes may include:

  • Dimpling of the skin, with a texture like orange peel
  • Nipple retraction, where the nipple turns inward instead of outward
  • Enlarged lymph nodes in the armpit

One type of breast cancer, inflammatory breast cancer, does not usually cause a lump. Instead, you may see redness, swelling, and sometimes a rash on the skin of the breast.

Signs of Benign Breast Masses

In contrast to breast cancer tumors, benign lumps are often squishy. They may feel like a soft rubber ball with well-defined margins. They're often easy to move around (mobile) and may be tender.

Infections in the breast can cause redness and swelling. Sometimes it can be difficult to tell the difference between mastitis (inflammation of breast tissue) and inflammatory breast cancer, but mastitis often causes symptoms of fever, chills, and body aches. Those symptoms aren't associated with cancer.


There are often differences in the way benign and cancerous breast lumps feel. Benign lumps are softer, squishy, and tend to move around. In most cases, cancerous lumps are hard and stay put when you feel them. The nipples and skin may look different around them.

Appearance on a Mammogram

Cancerous and benign masses may appear similar on a mammogram. However, some findings are more common in one than the other.

It's important to note that around 20% of breast cancers don't even show up on a screening mammogram. On the other hand, benign breast changes sometimes look like cancer.

Mass Due to Cancer

A breast cancer tumor on a mammogram is often irregular. The edges don't look smooth. A spiculated breast mass, with spikes that extend out from the main mass, is a strong signal that suggests cancer.

In fact, the word "cancer" is derived from how these crab-like extensions look as they invade nearby tissues. The edges of the mass also may appear fuzzy or indistinct.

Cancers often appear bright when looking at mammogram pictures. The area around the mass may be distorted. Breast calcifications (calcium deposits in the breast), especially when grouped in clusters, may be visible as well.

Mass Due to Benign Conditions

On a mammogram, benign tumors often appear round or oval (ellipsoid) with clear, well-defined edges.


Benign conditions such as breast adenosis (numerous and enlarged milk glands), fat necrosis (damage to fatty breast tissue), and radial scars (growths that look like scars when magnified) may look very similar to cancers on a mammogram.

Appearance on an Ultrasound

Breast ultrasound can detect some lumps that a mammogram cannot. It is also used to help diagnose masses found on a mammogram.

Ultrasound can help tell the difference between fluid-filled cysts, which aren't likely to be cancerous, and hard cysts that need further testing. Hard cysts are more likely to be cancerous.

On an ultrasound report, the term "hypoechoic" refers to an area that appears darker in the images. This means the area is solid.

Mass Due to Cancer

On ultrasound, a breast cancer tumor is often seen as hypoechoic. It has irregular borders, and may appear spiculated. Other ultrasound findings that suggest breast cancer include:

  • Nonparallel orientation (not parallel to the skin)
  • A mass that is taller than it is wide
  • Acoustic shadowing (a finding that indicates a solid mass)
  • Microlobulation (groups of small lobes on the surface of a solid mass)
  • Ductal extension (a breast duct widens and the wall thickens)
  • A branching pattern
  • A mass within a cyst
  • Angular margins (an irregular or jagged appearance)

Mass Due to Benign Conditions

With benign masses, a fluid-filled cyst may be noted. Solid benign masses usually:

  • Are uniform
  • Are oval
  • Have a clearly defined capsule
  • Are parallel to the skin
  • Have three or fewer groups of small lobes

Appearance on an MRI

A breast magnetic resonance imaging (MRI) scan can sometimes provide a clearer, more precise view than a mammogram to determine if a mass is cancerous or benign. That's especially true in women who have dense breasts.

During a breast MRI, a contrast agent is injected into the bloodstream. When this contrast "lights up" a region on the image, the region is said to be enhanced.

Malignant Breast Tumor

Cancerous masses on MRI differ both in how they look and the length of time they appear (kinetics). Because a cancerous mass often has irregular or spiculated borders, the internal divisions will become enhanced. A brighter rim on the outside of the mass is also common.

Cancerous tumors also often have what's called rapid signal intensity. This means they light up quickly from the contrast when the image is taken, but then wash out (dim) rapidly too.

Benign Breast Tumor

On an MRI, benign breast masses often have smooth borders or are lobulated. Any enhancement is usually minimal or patchy. The rise in signal intensity is slow, meaning the image becomes bright very slowly and it doesn't wash out.


Breast masses have distinct qualities when viewed by using mammogram, MRI, or other imaging techniques. They include the shape of the mass and the form of its borders, and how it compares with the other tissue around it.

Appearance with a Biopsy

When a breast biopsy is done, tissue is removed and sent to a pathologist. They will look at it under a microscope. Usually, special genetic studies are done as well.

The pathologist looks at the size and shape of the cells, as well as their arrangement if the tissue sample was taken by using a core needle biopsy. That's also true for an open biopsy done by making a cut through the skin to remove the sample.

Breast Cancer Tumor Cells

Under the microscope, breast cancer cells may appear similar to normal breast cells. They also may look quite different, depending on the tumor's growth and grade.

Cancer cells differ from normal cells in many ways. The cells may be arranged in clusters. They also may be seen invading blood vessels or lymphatic vessels.

The nucleus (center) of cancer cells can be striking, with nuclei that are larger and irregular in shape. These centers will stain darker with special dyes. Often, there are extra nuclei rather than just one center.

Benign Breast Mass Cells

Benign breast cells may or may not look identical to normal breast cells, depending on the type of mass, but neither do they look like cancer cells.


When necessary, a biopsy is done of the breast tissue that's causing concern. This means a sample is taken out, either by using a needle or through a cut in the skin. The sample cells are examined under a microscope to determine if cancer is present or not.


Breast changes are common. Many women find it helpful to know the differences between breast cancer tumors and benign breast masses, including what they feel like on a breast exam.

However, a healthcare provider should evaluate and diagnose any changes that cause you concern. Beyond a physical exam, they may use mammograms, MRIs, and ultrasound to help with the diagnosis. A breast biopsy may be needed on the basis of these other findings.

A Word From Verywell

Although breast changes during the course of a woman's life cycle are normal, it can be worrying to find a lump and have to wait to find out if it means cancer. If you find a lump, contact your healthcare provider right away. An early diagnosis is the best way to have a good outcome.

Frequently Asked Questions

  • Can a benign breast tumor become malignant?

    No, a benign breast tumor cannot become malignant. It will not perform metastasis, which is the process of cancer spreading to nearby tissues and organs to form new tumors. A breast specialist may recommend removing the benign tumor if it threatens to push against internal structures and cause damage.

  • Where is breast cancer usually located?

    Breast cancer is usually located in the ducts and lobules of the breast, although it can start in different areas, including the connective tissue. The tumors that grow from these types of breast cancer are reflected in their names: invasive ductal carcinoma and invasive lobular carcinoma. These can spread to nearby breast tissues, and from there, move into other areas of the body.

  • Can cancerous breast tumors be prevented?

    Cancerous breast tumors cannot be completely prevented, but maintaining a healthy lifestyle can lower your risk. Being physically active and eating a diet with lots of whole foods, like fresh fruits and vegetables, can reduce your risk of cancer. Getting recommended breast cancer screenings can help spot any cancers at an early, more treatable stage.

  • Is a breast nodule the same as a mass?

    Yes, a breast nodules is the same as a mass. These terms are used interchangeably. They can be hard like a rock or similar to a cyst and filled with fluid. If large enough, they can be felt during a routine self-exam or a clinical exam. The benign lumps sometimes resolve on their own. A solid growth of healthy cells, called a fibroadenoma, is noncancerous and common in younger women.

  • What is the difference between a tumor and a cyst?

    Tumors and cysts are two distinct entities.

    Tumors form when cells continue growing despite being told by the body to stop. They can be benign (noncancerous) or malignant (cancerous).

    Cysts are filled with air, pus, or fluids, and are usually benign. However, hard cysts have a higher chance of being malignant than cysts filled with fluid.

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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.
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Additional Reading
Originally written by Pam Stephan
Pam Stephan is a breast cancer survivor.
Learn about our editorial process