What Percentage of Breast Biopsies Are Cancer?

Here is what to know about breast biopsy results

Your doctor may order a breast biopsy after a screening tool such as a mammogram, ultrasound, or MRI shows something unusual in the breast; you find a lump in your breast; you experience changes in the nipple or breast skin; or you notice an unusual nipple discharge. Breast biopsies determine if the suspicious finding is actually cancer, and they can also determine the type of cancer, which can help you and your care team decide on a course of treatment. There are a few different kinds of biopsies; your doctor will determine the right one for you.

Research done by BCRF and other institutions is helping to improve the accuracy of diagnosis, which can lead to people getting the most effective treatments, in turn improving patient outcomes.

Here we discuss what percentage of breast biopsies are cancer, the factors influencing the results of biopsies, and what happens after a breast biopsy shows cancer.

Cancer diagnosis rates in breast biopsies

First, it’s important to keep in mind that millions of women get mammograms every year, and the vast majority show nothing suspicious. Only about 1.5 to 2 percent of mammograms necessitate a biopsy. So, what percentage of breast biopsies are cancer? The number there is also small: About 20 percent of women who undergo a biopsy will receive a cancer diagnosis. This means that most women will receive a benign result.

Research suggests that age and factors such as family history may influence if a biopsy shows cancer.

Understanding what happens during a breast biopsy

In a biopsy, a doctor will take a small sample of tissue or fluid from your breast and send the results to a pathologist, who will examine the sample under a microscope to see if it contains cancer cells. It can be an outpatient procedure that only takes an hour or two, or it may take up to six hours if surgery is needed (though this is rare). Your doctor may use an ultrasound or other imaging tool to confirm exactly from where the sample needs to be taken.

There are three main types of breast biopsies:

• Fine needle aspirations: The doctor will use a very thin needle and a syringe to take out the tissue or the fluid sample. You may receive local (topical) anesthesia before the procedure, and there are no stitches, though you may experience some soreness after the procedure. This is the least invasive form of biopsy.

• Core needle biopsies: Your doctor uses a wider needle to produce a larger tissue sample and may take several samples. After the removing the sample, your doctor will insert a small metal or titanium clip where the biopsy was so that it can be found during subsequent mammograms. As with a fine needle aspiration, you may receive local anesthesia and won’t need any stitches, but you may experience soreness afterwards.

• Surgical biopsies: These can reveal more than needle biopsies because they are larger samples of tissue. There are two kinds of surgical biopsies: incisional and excisional. In an incisional breast biopsy, the surgeon removes only the suspected affected area. In an excisional biopsy, the surgeon removes the suspicious area as well as any normal tissue surrounding it so that most (if not all) of the cancer cells have been removed. Your doctor may implant a wire or a magnetic or radioactive pellet into the area before the procedure to help guide the surgery. The procedure is typically performed under local anesthesia and requires stitches.

If you have a rash on your breast, your doctor may order a skin punch biopsy, which removes a sample of tissue from deep in the skin to rule out inflammatory breast cancer or other breast cancers that affect the skin.

It usually takes anywhere from a few days to about a week for your biopsy results to come back.

The role of age in breast biopsy results

There is some research on breast cancer biopsy results by age that suggests readings showing cancer increase with age. While breast cancer can occur at any time in life, the risk of a diagnosis increases the older you get. Most breast cancer diagnoses occur in women ages 55 and older, with the median age at the time of breast cancer diagnosis being 62. The highest rates of breast cancer occur in women in their 70s.

Research also suggests that age may affect the kind of cancer detected by biopsy. Another study found that the frequency of invasive cancer increased for biopsies in women between the ages of 40 and 49 and then again in women ages 60 to 69. Family history of breast cancer and having dense breasts can also influence breast biopsy results.

What happens after a breast biopsy shows cancer

After a breast biopsy shows cancer, a doctor will explain the results, what they mean, and how you can navigate what comes next. Biopsies can help determine the grade and subtype of the breast cancer as well as provide some information on the stage of the disease. This will guide treatment recommendations, but you may need more tests (like imaging scans) to learn more about the cancer. You’ll usually meet with specialists, such as a surgeon or oncologist, who will work together to recommend the next best steps. They might recommend surgery, medicine, or radiation, but treatment does not usually start right away. There is time to ask questions, understand your options, and get additional support.

Non-cancerous breast biopsy findings

Given that the percentage of breast biopsies that are cancer is about 20 percent, more often than not, biopsy results are benign. The most common benign findings include benign breast tumors, cysts, fibrosis, and calcium deposits:

• Benign breast tumors are called adenomas; the most common form is called a fibroadenoma. These occur most frequently in women under the age of 35.

• Cysts are fluid-filled sacs that, unlike breast cancer tumors, are mobile. These are also very common, and tend to occur in women between the ages of 35 and 50. They are likely to become larger and/or more tender close to a woman’s monthly period.

• Fibrosis is thickening of the breast tissue that’s usually caused by hormonal changes.

• Calcium deposits in breast tissue are usually noncancerous and can be associated with fibroadenomas or cysts.

The importance of early detection and screening

Biopsy results that reveal breast cancer are unsettling, but they can be life-saving. It’s well-established that earlier diagnosis leads to better outcomes for patients, and regular screenings and the biopsies that may result are the most effective way to catch cancer in its beginning stages. Early detection means that the cancer is easier to treat and increases the chances of survival.

How often to screen for breast cancer depends on age and family history of breast cancer, which can raise a woman’s risk. Current screening guidelines recommend that women who are at an average risk for breast cancer start getting mammograms every two years beginning at age 40. Women at higher risk should begin earlier and have yearly screenings.

Moving forward: Early detection and BCRF’s role in advancing research

The likelihood of a breast cancer biopsy showing cancer increases with age, so it’s important to keep up with regular screenings. Remember that if you are one of the 20 percent of women who do receive a cancer diagnosis after a biopsy, there may be a number of treatment options available—depending on the characteristics of the tumor—and that number is always increasing thanks to research. The more we know about how cancer behaves, the more precisely treatments can be targeted to attack the cancer and reduce side effects.

Research funded by BCRF continues to play a vital role in improving biopsy technology in particular. In the last few years, our researchers have helped expand the potential of liquid biopsies, which are blood tests used to detect circulating tumor cells. Previously, liquid biopsies had only been able to confirm that a cancer is late stage, but BCRF researchers have developed a version that can also assess the blood sample for factors that are related to early-stage cancer. Exciting innovations like these are all possible thanks to research.

Frequently asked questions about breast cancer biopsies 

1. What are the odds that a breast biopsy is cancerous?

Approximately 20 percent of breast biopsies lead to a cancer diagnosis, although this can vary depending on individual risk factors.

2. How does age affect the likelihood of cancer in breast biopsies?

Cancer diagnosis rates tend to increase with age, with older populations having higher percentages of biopsy results revealing cancer.

3. What is the most common diagnosis from a breast biopsy?

The most common findings are benign conditions, such as fibrocystic changes or other non-cancerous abnormalities.

4. What happens if a breast biopsy is positive for breast cancer?

If a biopsy returns a positive result for cancer, your doctor will discuss the next steps, including treatment options and further testing.

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