Granulomatous mastitis (GM) is a rare breast condition that can sometimes be mistaken for breast cancer. GM can cause a breast lump that might raise concern during a breast self-exam.

Instead of ignoring a breast lump or assuming it’s something benign (noncancerous), such as GM, always tell your doctor about any breast changes you notice. Your doctor can guide you through the diagnostic process to find out whether a lump is benign or caused by cancer.

Keep reading to find out about key differences between breast cancer and granulomatous mastitis, plus tips for getting the right diagnosis.

What Is Granulomatous Mastitis?

Granulomatous mastitis is a chronic, benign breast condition that causes inflammation. Before more testing is done, healthcare providers may first suspect inflammatory breast cancer or mastitis (a breast infection).

Granulomatous Mastitis Causes

There are two main types of granulomatous mastitis — idiopathic and infectious.

Researchers aren’t sure what causes idiopathic GM or why it develops, but some believe it may be an autoimmune response to breast irritation. An autoimmune response happens when the immune system, which typically protects the body from illness, mistakenly attacks healthy tissue.

Infectious granulomatous mastitis can be caused by bacteria, fungi, and mycobacteria, particularly those linked to opportunistic infections (infections that happen more easily in people with weakened immune systems).

Granulomatous Mastitis Symptoms

Many GM symptoms overlap with symptoms of breast cancer, especially IBC. GM symptoms can last for a few months and may include:

• One or more tender or painful breast lumps
• Tender or painful lumps in the armpit
• Breast skin inflammation
• Inverted nipple
• Breast swelling and discoloration
• Abscesses (pockets of pus) or lesions (sores) on the breast skin
• Skin fistulas
• Pitted breast skin
• Systemic symptoms (symptoms that affect other parts of your body), such as joint pain

Some of these symptoms are also common in inflammatory breast cancer. Although IBC doesn’t always cause a breast lump, it often causes breast swelling, discoloration, pitted skin, and an inverted nipple. These overlapping symptoms can make it easy to mistake granulomatous mastitis for IBC.

What Are the Key Differences Between Granulomatous Mastitis and Breast Cancer?

Although granulomatous mastitis and breast cancer share some symptoms, there are several important differences between the two conditions.

Risk Factors

Risk factors for GM and breast cancer are different. Granulomatous mastitis is most common in reproductive-aged women who have given birth and breastfed, and it rarely affects men, according to Breast Cancer Now. You may also be at a higher risk for GM if you’ve taken hormonal contraceptives or have diabetes or an autoimmune disease, such as lupus or psoriasis.

Breast cancer risk increases with age, and most cases are diagnosed after age 50. Pregnancy affects breast cancer risk differently than GM — you’re more likely to develop breast cancer if you’ve never been pregnant or if you had your first pregnancy after age 30. Women have a much higher risk of breast cancer than men, according to The University of Texas MD Anderson Cancer Center.

Prognosis

Granulomatous mastitis is a non-life-threatening condition that in some cases may improve without treatment. However, you should still tell your doctor about any symptoms or breast changes you notice. Infectious GM needs treatment that targets the cause of the infection.

Your specialist can tell you whether you need treatment based on your symptoms. Treatment won’t cure idiopathic GM, but it can help relieve symptoms. Granulomatous mastitis can also recur (come back), so tell your doctor if symptoms return.

Breast cancer can be life-threatening. Prognosis can vary widely depending on the type and stage of cancer.

The five-year relative survival rate — the percentage of people who are still alive five years after diagnosis, compared with the overall population — is above 99 percent when breast cancer is found and treated early. The rate drops to 31 percent when the cancer has spread to other parts of the body.

Prognosis also depends on the type of breast cancer, whether it has spread to nearby lymph nodes, and how well it responds to treatment. Breast cancer can also recur, even after successful treatment.

Does GM Raise Your Risk of Breast Cancer?

It’s important to know that granulomatous mastitis doesn’t raise your risk of breast cancer. However, it’s possible to have both conditions at different times or even at the same time in the same breast.

Always tell your doctor about any new breast changes. Never assume you know what’s causing a new symptom.

How Is Granulomatous Mastitis Treated?

Granulomatous mastitis usually requires a different treatment approach than breast cancer, although some treatments may be used for both conditions. GM can be challenging to treat, so you may need to try more than one treatment option before finding what works best for you.

Depending on the cause, GM treatment often starts with antibiotics, antifungal medications, or antimycobacterial drugs. Doctors may also prescribe anti-inflammatory medications, such as corticosteroids, to help reduce swelling and pain.

In some cases, surgery may be needed to drain an abscess or remove damaged tissue. However, surgery such as lumpectomy (removal of a breast lump) isn’t considered a standard GM treatment and is usually avoided when possible.

Lumpectomy is also commonly used to remove breast tumors. Although it’s not usually used for inflammatory breast cancer, it may be an option for other types.

Getting the Correct Diagnosis

Receiving the correct diagnosis ensures you get the right treatment for either granulomatous mastitis or breast cancer. Because the two conditions can look alike, one of the most important steps is telling your doctor about any breast changes as soon as you notice them.

You might first notice breast swelling or a lump during a breast self-exam. Regular self-exams can help you spot changes early because they help you learn how your breasts normally look and feel.

After examining your breasts, your doctor may recommend tests to help tell the difference between granulomatous mastitis, breast cancer, and other breast conditions. Diagnosing GM and breast cancer may include the following steps:

Imaging Scans

You may need imaging scans from a breast radiologist. These tests give doctors a closer look inside the breast to check for tumors, inflammation, or other changes.

Common breast imaging tests include mammograms (breast X-rays) and breast ultrasound imaging, which uses sound waves to produce images of breast tissue. Research suggests that ultrasound imaging may be especially helpful for telling the difference between GM and breast cancer.

Mammograms can be uncomfortable for people with granulomatous mastitis because the breast may be extra tender. Also, mammograms may show only general signs of GM, such as uneven breast density. In some cases, doctors may use MRI scans to look for signs of breast disease.

Imaging test results aren’t always enough to confirm a diagnosis, so more testing is usually needed to determine whether you have granulomatous mastitis or breast cancer. Because GM is rare and not always recognized right away, diagnosis can sometimes take longer.

Biopsy

A breast biopsy can help confirm whether you have granulomatous mastitis or breast cancer. During a biopsy, a doctor removes a small sample of tissue from the affected breast to examine under a microscope.

In many cases, doctors use ultrasound-guided breast biopsies to collect the tissue sample. Sometimes, a biopsy may be done during the first ultrasound appointment to help speed up diagnosis. In cases of GM and IBC, a skin biopsy may also be needed.

Your doctor will go over your biopsy results with you and explain what they mean. Together, you and your healthcare team can decide on the best treatment plan based on your diagnosis.

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