Important Facts About Breast Cancer Tumors

Cancerous vs Benign Breast Masses on Palpation, Imaging, and Biopsy

woman pointing to a breast mass that's a breast cancer tumor
Lester Lefkowitz / Getty Images

How do breast cancer tumors differ from a mass in the breast due to another cause? Differences between benign and cancerous breast lumps can include how they feel, with breast cancers often hard and immobile and benign tumors softer, round, and mobile. They can also look different on mammograms, with cancers often appearing spiculated and irregular and benign tumors round or oval and well-defined. There are differences that can be noted on breast MRIs and ultrasound as well. That said, breast cancer tumors and benign breast masses can sometimes both feel similar and look alike on imaging tests, and a biopsy may be needed to tell them apart.

Cancerous vs Non-Cancerous Breast Tumors (Masses)

There are many ways that breast cancer tumors and benign masses differ, and we will take a look at these with respect to palpation (how a lump feels), and how they appear on mammograms, MRI, and ultrasound. (The different types of breast cancer may also differ considerably in these areas.) That said, there are a number of benign breast lesions that mimic breast cancer and this is one of the reasons a doctor may recommend a needle biopsy, core biopsy, or open biopsy, even if she is fairly certain of the diagnosis. In addition, the different

What a Breast Tumor Due to Cancer Feels Like

How a breast mass feels can give doctors a fairly good idea whether a lump is a breast cancer tumor or a benign mass. In one study, palpation (feeling the lump) had an overall accuracy of around 90 percent.

Palpation of Cancerous Masses

Masses in the breast that are cancer are often very firm, like a rock or a carrot, and have an irregular shape and size. They are also often fixed (feel like they are attached to the skin or nearby tissue so that you can't move it around by pushing on it), but may be mobile as well. They are more likely to be non-tender, but some breast cancers can cause breast pain.

On exam, other changes may be present as well, such as dimpling of the skin or an orange-peel appearance, nipple retraction, or enlarged lymph nodes in the armpit.

One type of breast cancer, inflammatory breast cancer, does not usually cause a lump, but instead involves redness, swelling, and sometimes a rash on the skin of the breast.

Palpation of Benign Breast Masses

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

Breast infections, can cause redness and swelling. Sometimes it can be difficult to distinguish mastitis and inflammatory breast cancer, but mastitis often causes symptoms of fever, chills, and body aches as well.

Appearance of Cancerous Breast Masses on Mammogram

Like a physical examination, there can be overlap between cancerous and benign masses on mammogram, but some findings are more common with each. It's important to note that around 20 percent of breast cancers do not show up on a screening mammogram. Similarly, benign breast conditions may appear like cancer.

Mass Due to Cancer

A breast cancer tumor on mammogram is often irregular, and the edges do not appear smooth. A "spiculated" breast mass is often highly suggestive of cancer, and describes a mass that appears star-like, with tentacle-like areas extending out from the main mass. In fact, the word cancer derives from the word crab, based the appearance of these crab-like extensions that penetrate out from the main mass and invade nearby tissues. The edges of the mass may also appear fuzzy or indistinct.

When looking at mammogram pictures, cancers often appear bright and the area around the mass may be distorted. Breast calcifications, especially calcifications in clusters may be noted.

Mass Due to Benign Conditions

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


Benign conditions such as breast adenosis, fat necrosis, and radial scars may look very similar to cancers on a mammogram, with spiculated masses or microcalcifications.

Appearance of Breast Cancer Tumors on Ultrasound

A breast ultrasound is a helpful test in distinguishing between solid and cystic masses. In looking at an ultrasound report, the term "hypoechoic" refers to an area on the study that appears darker, and means the area is solid.

Mass Due to Cancer

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

  • Non-parallel orientation (not parallel to the skin)
  • A mass that is taller than it is wide
  • Acoustic shadowing
  • Microlobulation
  • Duct extension
  • A branch pattern
  • A mass within a cyst
  • Angular margins, which means an irregular or jagged appearance to the mass

Mass Due to Benign Conditions

With benign masses, a fluid filled cyst may be noted. Areas that are dark (solid) are usually uniform, oval in shape, have a clearly defined capsule, are parallel to the skin, and have three or fewer lobulations. If a cyst is suspected, needle aspiration of the cyst can often result in the cyst disappearing completely.

MRI Appearance

A breast MRI can sometimes provide better distinction between masses due to cancer and those related to benign causes than a mammogram, especially in women who have dense breasts. During a breast MRI, a contrast agent is injected into the bloodstream. When this contrast "lights up" on the image, the region that lights up is said to be enhanced, and appears brighter than the surrounding tissue

Malignant Breast Tumor

Cancerous masses on MRI differ both in general appearance, and the length of time they appear (kinetics). On MRI, a cancerous mass often has irregular or spiculated borders with internal septation that enhances. Rim enhancement (brightening) on the outside of the mass is also common. Cancerous tumors also often have rapid signal intensity. In lay man's terms, this means that the areas that are cancerous light up rapidly from the contrast when the image is taken, but then wash out rapidly (turn less bright) rapidly as well.

Benign Breast Tumor

On MRI, benign breast masses often have smooth borders or are lobulated. If enhancement of the mass is present, it is usually minimal or patchy. The rise in signal intensity is slow (the image becomes bright only very slowly), and doesn't wash out (it stays bright).

Appearance on Biopsy

When a breast biopsy is done, tissue is sent to a pathologist to look at under a microscope (and special molecular studies are usually done as well). The pathologist will look at the size and shape of the cells as well as the arrangement of cells (this can be seen on a core biopsy or open biopsy but not on a needle biopsy specimen).

Breast Cancer Tumor Cells

Under the microscope, breast cancer cells may appear similar to normal breast cells (well-differentiated) or very little like breast cancer cells (poorly differentiated) depending on the tumor grade. Cancer cells differ from normal cells in many ways.

The cells may be arranged in clusters, and may be seen invading blood vessels or lymphatic vessels. The nucleus of cancer cells can be striking, with nuclei that are larger, irregular in shape, and stain darker with special dyes. There are also often extra nuclei (rather than just one) present.

Benign Breast Mass Cells

Benign breast cells may look identical to normal breast cells, or different, but non-cancerous depending on the condition.

A Word From Verywell

Looking at the differences in breast cancer tumors and benign breast masses on exam as well as imaging studies can help you understand why these tests are done. Knowing the limitations and how there are exceptions to all of these "general rules," however, can help you understand why a doctor may sometimes recommend a breast biopsy even if findings strongly suggest that a mass is either benign or malignant.

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