Health Conditions A-Z Skin, Hair & Nail Conditions 7 Causes of Lumps in Your Armpit By Dr. Roshini Raj Dr. Roshini Raj Roshini Raj, MD, is Health's former magazine's medical editor and coauthor of What the Yuck?!. Board-certified in gastroenterology and internal medicine, Dr. Raj is a Clinical Associate Professor of Medicine at New York University Medical Center, a contributor on the Today show, and a co-founder of the Tula skin care line. health's editorial guidelines Updated on April 13, 2024 Medically reviewed by Doru Paul, MD Medically reviewed by Doru Paul, MD Doru Paul, MD, is a board-certified oncologist and hematologist. He is an associate professor of clinical medicine at Weill Cornell Medical College. learn more Close triocean/Getty Images Finding a lump in your armpit can be worrisome, especially if it's painful or appears unexpectedly. The lump could be a sign or symptom of conditions like breast cancer or hidradenitis suppurativa, but it might also emerge because of shaving or as a vaccine side effect. These types of lumps additionally will go away on their own or with treatment. Read on to learn about armpit lumps, including how they're diagnosed and treated and when to see a healthcare provider. What Causes Lumps in Armpits? In general, a person could experience armpit lumps due to: Cysts—fluid-filled tissue pockets Infections Swollen lymph nodes—small structures that are part of the immune system 1. Breast Cancer Lumps or swelling in the armpit can be one of the symptoms of breast cancer. The lumps may be the result of breast cancer spreading to armpit lymph nodes. It is important to note, though, that changes related to the breast are more often not associated with cancer. Updated Screening Guidelines In 2024, the U.S. Preventive Services Task Force (USPSTF) released new guidelines recommending that women get screened for breast cancer every other year between the ages of 40 and 74. Some women may need an annual screening, especially if you're at a higher risk of breast cancer or if you have dense breast tissue. 2. Breast Infections Like breast cancer, breast infections—which are breast tissue infections caused by bacteria—can lead to swollen armpit lymph nodes. Other signs of a breast infection include: Breast lumps and pain Breast tissue swelling, tenderness, and warmth Fever Flu-like symptoms Itchiness Nipple discharge One-sided breast enlargement or fullness Skin redness 3. Cat Scratch Disease Sometimes, cat saliva can contain infection-causing bacteria. When a cat with this bacteria in their saliva bites, licks, or scratches you, the resulting infection is called cat-scratch disease. You could end up with a lump in your armpit from lymph node swelling if a scratch or bite occurs on your arm. 4. Cysts Cysts can appear in your armpit and cause lumps after you've shaved. You can also develop armpit lumps from antiperspirants—products that reduce how much you sweat—but not deodorants. 5. Hidradenitis Suppurativa Painful lumps within the skin, including in your armpit, can be a sign of hidradenitis suppurativa (HS). The lumps commonly occur where one part of your skin touches another. HS can sometimes have the same appearance as acne and pimples, but they are different skin conditions. 6. Lipoma It may be a lipoma if your lump isn't red, inflamed, or filled with pus. Lipomas are noncancerous, fatty tissue tumors. While you can get lipomas at any age, they mostly form in adults between 40 and 60. There is no known cause of them other than possibly your genetics. 7. Vaccines Lymph nodes in your armpit can also become swollen due to vaccines as part of an immune response. For example, Gardasil—the vaccine for human papillomavirus (HPV), a set of viruses that can lead to some types of cancer—lists swollen lymph nodes as a side effect. COVID-19 vaccines may also lead to swollen lymph nodes. One study found that 44% of participants experienced swollen lymph nodes in their armpits after receiving the COVID-19 vaccine. Diagnosing Armpit Lumps To diagnose armpit lumps, a healthcare provider will do a physical exam, which typically involves gently pressing on the lump. The provider will also likely ask you questions to get more information, such as when you noticed the lump or if anything makes it worse. Other tests may be necessary based on what the provider finds during the physical exam, such as: Biopsies, where providers get a sample of tissue for lab examination Imaging tests, like X-rays and magnetic resonance imaging (MRI) scans, to get pictures of soft tissues Swab tests for sores or wounds that are leaking fluid to determine if you have an infection Treating Armpit Lumps Treatment for lumps in the armpit will depend on what caused the lump. For example, you may have to avoid shaving or switch antiperspirants. Some lumps might also require surgical removal—like in the case of lipomas—while others can go away over time if they're a vaccine side effect. When To Contact a Healthcare Provider A lump in your armpit doesn't always have a serious cause. Talk to a healthcare provider if you experience armpit lumps or swollen lymph nodes in the armpits: Accompanied by fever, night sweats, or unexplained weight loss That are unexplained That feel hard, have grown larger, or have worsening pain That could be a potential breast cancer sign With an irregular shape or in a fixed position A Quick Review Causes of lumps in the armpit generally include cysts, infections, and swollen lymph nodes. Some armpit lumps may be harmless—resulting from actions like shaving or using antiperspirants—while others can be a potential sign of breast cancer or infections. The diagnosis for armpit lumps can include physical exams and testing, and treatment for these types of lumps will vary based on the cause. See a healthcare provider if you have concerns about armpit lumps and if you have additional symptoms like pain and night sweats. Frequently Asked Questions When should I worry about a lump in my armpit? Unexplained lumps or lumps with symptoms like fever and weight loss or that feel progressively painful are a few reasons to be worried about an armpit lump. What does a cancerous lymph node in your armpit feel like? Lymph nodes can swell, making them easier to feel in some cases, but ones that are cancerous may look and feel normal. The only way to know if you have cancerous lymph nodes, however, is for a healthcare provider to do a biopsy. Can deodorant cause lumps under the armpit? Deodorant doesn't cause lumps in the armpit. Was this page helpful? Thanks for your feedback! Tell us why! Other Submit 14 Sources Health.com 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. MedlinePlus. Armpit lump. American Cancer Society. Breast cancer symptoms: what you need to know. U.S. Preventive Services Task Force (Task Force). Breast cancer: Screening. MedlinePlus. Breast infection. American Academy of Family Physicians. Cat-scratch disease (cat-scratch fever). American Academy of Dermatology. Hidradenitis suppurativa. American Academy of Orthopaedic Surgeons. Lipoma. Ho TC, Shen DHY, Chang CC, et al. Immune response related to lymphadenopathy post COVID-19 vaccination. Vaccines (Basel). 2023;11(3):696. doi:10.3390/vaccines11030696 MedlinePlus. HPV - also called: human papillomavirus. National Library of Medicine DailyMed. Gardasil 9- human papillomavirus 9-valent vaccine, recombinant injection, suspension. Wolfson S, Kim E, Plaunova A, et al. Axillary adenopathy after covid-19 vaccine: no reason to delay screening mammogram. Radiology. 2022;303(2):297-299. doi:10.1148/radiol.213227 American Academy of Dermatology. Hidradenitis supprativa: diagnosis and treatment. MedlinePlus. Swollen lymph nodes. American Cancer Society. Lymph nodes and cancer.