Understanding Breast Lumps - Benign and Cancerous

Breast Lumps - When are They Cancer and When are They Not?

Computer rendering of breast cancer
What do you need to know about benign and cancerous breast lumps?. MedicalRF.com/Getty Images

What is the difference between a benign (non-cancerous) breast lump and a malignant (cancerous) breast lump?


During a breast self-exam, you may notice lumps or a change in breast texture. This can be terrifying (we all seem to know of at least one person who has had breast cancer) but not all lumps are cancerous.

If you do find a lump, however, it's important to see your doctor right away. Unfortunately, it can sometimes be difficult to determine whether a lump is benign or malignant, and the only way to know for certain is through further tests, for example, a mammogram, ultrasound, MRI, or biopsy.

You may be very frightened to take these steps to figure out what is going on in your breast, but keep in mind that even in the worst case scenario, that is breast cancer, most tumors are very treatable.

Let's take a look at a few of the most common non-cancerous breast Lumps—cysts and fibroadenomas—as well as cancerous breast lumps. Distinguishing between cancerous and non-cancerous tumors is not always as black and white as it sounds. Let's first talk about some of the important differences, and why it can take some time to determine exactly what kind of tumor you have.

Benign vs Malignant Tumors

Many people are frustrated that it's not easier to quickly differentiate a benign breast tumor from a malignant breast tumor. How are they similar and how are they different?

Both benign and malignant breast tumors can grow quite large. Though in general, you may have heard that cancerous breast lumps are painful whereas benign ones hurt, this is not always the case.

In other words, cancer can be painful and benign tumors painless. both benign tumors and malignant tumors can recur (come back) when they are removed, though benign tumors always come back in the same location and malignant tumors can recur locally or in other regions of the body

The hallmark of malignant tumors is that they can spread to other regions of the body (metastasize) whereas benign tumors cannot.

Normal tissues have chemicals which act like glue, keeping them stuck together. Cancerous cells lack these "adhesion chemicals" and are better able to break off and float away through the bloodstream or lymphatic system. Malignant tumors often invade nearby tissues, whereas benign tumors may push against nearby tissues but don't invade. The word cancer actually comes from the Greek word for "crab" which was used to describe the clawlike extension of cancers into surrounding tissue. 

Cancerous tumors tend to grow more rapidly than benign tumors, but this is not always the case. In fact, a breast cyst may pop up more suddenly than a cancerous tumor. The behavior of malignant tumors compared to benign tumors is related to the underly differences between normal cells and cancer cells.

Breast Cysts

A breast cyst is a benign (harmless) fluid-filled sac, which can grow right within the breast tissue. Breast cysts are very common and rarely linked to breast cancer.

What Does a Breast Cyst Feel Like?

This breast lump will feel smooth and squishy. If you are pressing on a cyst, it will have some give to it, like a water balloon. A cyst can move around and can change in size during your menstrual cycle.

Where are Breast Cysts Located?

Breast cysts can be located near the surface, or deeper inside, close to your chest wall. If the cyst is closer to the surface, it is easy to find and easy to distinguish from other lumps. But if it is deeper inside, it's more difficult to distinguish it from other kinds of breast lumps, because when you press on it, you're actually trying to work through layers of breast tissue, which may be dense and firm.

How are Cysts Diagnosed?

Cysts cannot be diagnosed by a clinical breast exam or mammogram alone. Instead, a doctor will probably order a breast ultrasound—since the sound waves pass right through fluid-filled cysts, as opposed to bouncing back in solid lumps.

In the case of solid cysts, more tests, such as a biopsy may be needed. (The term multiloculated cysts refers to lumps which have several pockets with solid tissue in between.)

In the case of a fluid-filled cyst, a doctor may also take a sample of the cyst fluid by performing a fine needle aspiration with a syringe. This procedure removes the fluid from inside the cyst. If the cyst deflates with aspiration, and the fluid is non-bloody, this is a benign breast cyst. 

Breast Fibroadenomas

Breast fibroadenomas are benign tumors consisting of glandular and connective tissue. That being said, while fibroadenomas are benign, complex fibroadenomas increase a woman's risk of developing breast cancer in the future by one and a half to two times. Breast fibroadenomas are most commonly found in women aged 35 or younger. Women who develop fibroadenomas over the age of 35 should make sure that appropriate studies are ordered to make sure their lump is "just" a fibroadenoma.

What does it feel like? A fibroadenoma will feel like a round breast lump and is often quite firm. It can usually be moved around beneath the skin during a breast self-exam.

Where is it? Fibroadenomas are often located near the surface of the breast and are easily felt.

Treatment: There are several different treatment options for fibroadenomas ranging from a lumpectomy to radiofrequency ablation, to high-frequency ultrasound, and more. There have been cases in which a biopsy has shown a fibroadenoma, but upon removal, there is evidence of both the fibroadenoma and breast cancer, so even with a biopsy, your doctor may recommend removing the fibroadenoma completely.

When does it appear? Fibroadenomas usually appear in women younger than 30, but they can appear in women of any age. They may occur during pregnancy. They are not common in post-menopausal women.

Other Lumps or Tumors

There are several other conditions which may cause a benign, precancerous, or cancerous breast lumps. Some of these include:

  • Ductal or lobular hyperplasia - Atypical lobular hyperplasia and atypical ductal hyperplasia are conditions which are considered precancerous. These lumps are not cancer, but significantly increase the risk that you could develop breast cancer. 
  • Lobular carcinoma in situ (LCIS) and Ductal carcinoma in situ (DCIS) - Both LCIS and DCIS are cancer, but since the tumors have not yet broken through something known as the "basement membrane" they are not considered invasive. (Stage I to IV of breast cancer are all considered invasive.) Carcinoma in situ is considered stage 0 cancer.
  • Adenosis is a benign condition in which there is enlargement in the lobules of the breast. Adenosis can cause a lump that feels like a cyst or a tumor and is sometimes hard to distinguish from a cancer, since it usually causes calcifications on a mammogram.
  • Phyllodes tumors - A phyllodes breast tumor is an uncommon tumor that can be either benign or malignant. Since benign phyllodes tumors have a tendency to become malignant, these tumors are treated in much the same way. Most breast cancers begin in cells called epithelial cells which form carcinomas. In contrast, phyllodes tumors occur in mesenchymal cells (connective tissue cells) and the tumors are actually sarcomas.
  • Intraductal papillomas - Intraductal papillomas are tumors which begin the in the milk ducts of the nipple and are most often noted by the presence of a nipple discharge. While these tumors are most often benign, if they have regions of atypical hyperplasia they may be associated with an increased risk of cancer.
  • Granular cell tumors
  • Fat necrosis and oil cysts - When the breasts are damaged by surgery or trauma, scar tissue may develop. Fat necrosis may occur which feels like a hard lump, or instead, benign

    oil cysts may occur

  • Mastitis - An infection of the breast, mastitis is often accompanied by redness, swelling, and pain. Sometimes it may be difficult to distinguish between mastitis and inflammatory breast cancer, a cancer which usually begins with redness, tenderness, and a rash, rather than a lump.
  • Duct ectasia - Mammary duct ectasia is a benign condition in which the milk ducts become clogged and swollen, often causing a grayish discharge. It may cause a small lump just under your nipple, and sometimes cause the nipple to be retracted inwards. It is most common in women who are around the age of menopause.
  • Radial scars - Radial scars are an uncommon condition which can be benign, precancerous, or cancerous. They do not usually cause a lump that you can feel but may appear as a lump on ​a mammogram.
  • Lipomas or other benign tumors or lumps like hamartomas, breast hematomas, hemangiomas, adenomyoeptheliomas, and neurofibromas
  • Metastatic cancer - On rare occasions, metastases from cancers in other regions of the body, such as colon cancer or lung cancer, may give rise to a new breast lump.

Remember only a breast biopsy can distinguish between a cancerous lump or tumor versus a benign breast lump or tumor. Also, it's important to note that certain benign breast conditions—like papillomas or atypical hyperplasia—may increase a woman's risk of developing breast cancer in the future. 

Breast Cancer

What is it? Breast cancer is a malignant lump that is made of abnormal breast tissue cells, growing in an uncontrolled way that may spread to the adjacent tissues or other organs.

What does it feel like? A malignant breast lump will have an irregular shape (though at times it can be round) with a pebbly surface, somewhat like a golf ball. It is often very hard, like a slice of raw carrot. It may not be movable during a breast self-exam, but since tissue around it may move, it's sometimes hard to know if the lump is moving, or if healthy tissue around it is moving. Most often a breast cancer is painless, though breast cancer can sometimes cause breast pain as well.

A clinical breast exam and a mammogram may help with the diagnosis, though sometimes an ultrasound or MRI are needed. Even with all of these imaging studies, however, it may be difficult to know whether a lump is benign or malignant. A biopsy is most often needed to provide more information about the lump and is the only way to distinguish between cancer and a non-cancerous condition.

Where is it? Breast cancer can be located near the surface, or deeper inside the breast, close to the chest wall. It can also occur in the armpit area, where there is more breast tissue (the "tail" of the breast.)

Treatment: The treatment for breast cancer depends on the stage at diagnosis. In addition to surgery, treatments may include chemotherapy, hormonal therapy, radiation therapy, targeted therapies, or new medications which are being studied in clinical trials.

When does it appear? Breast cancer may occur at any age from childhood into old age.


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