What Causes Hard Forearm Lumps & When to Seek Care
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Hard, small bumps on the forearm are most commonly caused by skin conditions that form cysts, warts, or abscess. A hard, painful lump on the forearm can be caused by trauma from an injury, or even an insect bite. Other less common causes include fatty tissue growth that forms a hard lump under the skin of the forearm. Learn more below about other causes and treatment options.
Hard lump on forearm explained
The forearm is a complex part of the body, allowing you to twist your arm during a tennis match or reach for your phone at work. A lump in this area can be concerning; however, there are many benign causes associated with this symptom.
The forearm is defined by the area in the upper limb between the elbow and wrist. The long bones of the forearm are called the radius and the ulna. It contains an anterior group of muscles that help flex the wrist and fingers and a posterior group of muscles that help extend the wrist and fingers. There are three primary nerves that run through the forearm called the radial, median and ulnar nerve, and two principal arteries in the forearm called the radial artery and ulnar artery.
Now that the normal structural characteristics have been detailed above, we can look into some possible characteristics of your hard forearm lump.
Common accompanying symptoms of a hard forearm lump
If you have a hard forearm lump, you may also experience:
- Pain or discomfort
- Tenderness to the touch
New lumps and bumps on the body are also concerning since they can be the initial sign of a cancerous process. However, there are signs and symptoms that are reassuring. Lumps in the forearm are less concerning if they have the following characteristics:
- Easily mobile
Lumps in the forearm that require care have the following characteristics:
- Rigid/stuck in place
- Grows in size over time
- Changes in color
Make an appointment with your physician if you experience these symptoms in order to get appropriate treatment.
What causes a lump on the forearm?
Any disease, damage, or injury to the structures of the forearm can result in a hard forearm lump. In addition to the muscles, nerves, and bones of the forearm, there are also various tendons, tissues, ligaments, and arteries throughout this area that can also cause lumps. Conditions can be most easily categorized as benign (noncancerous) or malignant (cancerous). The following details may help you better understand your symptoms; however, you should see a physician for a proper diagnosis.
There are various benign causes behind a forearm lump, including:
- Growths: Growths can occur in the muscle, soft tissue, and nerves of the forearm causing hard, sometimes large lumps. For example, a growth of nerves in the forearm can result in lumps as well as symptoms of pain or numbness.
- Dermatologic: There are many dermatologic conditions that can result in a hard lump in the forearm. For example, cysts are sacs that can be filled with fluid, air, or other material and can form in any part of the body. Cysts can occur in the forearm, causing pain or possible injury from inflammation.
- Inflammatory: This includes conditions such as infections, panniculitis, and even arthritis, which can result in multiple bumps in the forearm that can be red, fairly tender or painful. Panniculitis is a group of inflammatory diseases that affect the fatty tissue under the skin and result in skin nodules. Arthritis is a general term for multiple conditions that cause painful inflammation and stiffness throughout the body. Arthritis can result in thickening and swelling that can result in damage and deformity of the bones and cartilage in the form of nodules. See this image for a visual representation of arthritic nodules.
- Traumatic: Trauma to the forearm area from bumping a table, falling, or being in an accident can result in forearm lumps. Traumatic causes may also involve visible deformity or bleeding, depending on the severity of the trauma.
- Environmental: Insects are a nuisance in general, and are even more annoying when they bite you. A bite from any insect, such as a mosquito, spider, flea, etc., can cause a hard lump on the forearm that can also swell and become itchy and painful.
In general, any growth is the result of cells dividing and growing uncontrollably. Sometimes there is a genetic mutation in DNA or a specific protein that results in this unchecked growth. These abnormal cells accumulate to form a noticeable lump. A lump (also known as a tumor) can be benign and can arise from many of the causes above. However, if this lump grows and invades the body, it is considered malignant. For example, a rare type of cancer called sarcoma originates in the supportive, connective tissues of the body and can result in a hard forearm lump before or as it spreads.
This list does not constitute medical advice and may not accurately represent what you have.
A cyst is a small sac or lump, filled with fluid, air, fat, or other material, that begins to grow somewhere in the body for no apparent reason. A skin cyst is one that forms just beneath the skin.
It's believed that skin cysts form around trapped keratin cells – the cells that form the relatively tough outer layer of the skin.
These cysts are not contagious.
Anyone can get a skin cyst, but they are most common in those who are over age 18, have acne, or have injured the skin.
Symptoms include the appearance of a small, rounded lump under the skin. Cysts are normally painless unless infected, when they will be reddened and sore and contain pus.
Diagnosis is made through physical examination. A small cyst can be left alone, though if it is unsightly or large enough to interfere with movement it can be removed in a simple procedure done in a doctor's office. An infected cyst must be treated so that the infection does not spread.
Top Symptoms: skin-colored armpit bump, marble sized armpit lump, small armpit lump
Symptoms that always occur with skin cyst: skin-colored armpit bump
Urgency: Wait and watch
Lipoma is a word that translates as "fatty tumor," but a lipoma is not cancer. It is simply a growth of fat between the muscle layer and the skin above it.
The exact cause is not known. The condition does run in families and is associated with other unusual syndromes such as adiposis dolorosa, which is similar. Lipomas most often appear after age 40.
Symptoms include a soft, easily moveable lump beneath the skin, about two inches across. A lipoma is painless unless its growth is irritating the nerves around it. They are most often found on the back, neck, and abdomen, and sometimes the arms and upper legs.
It is a good idea to have any new or unusual growth checked by a medical provider, just to make certain it is benign.
Diagnosis is made through physical examination, biopsy, and imaging such as ultrasound or CT scan.
Most of the time, treatment is not necessary unless the lipoma is unsightly or is interfering with other structures. It can be removed through surgery or liposuction.
Top Symptoms: skin-colored groin bump, marble sized groin lump, small groin lump
Symptoms that always occur with lipoma: skin-colored groin bump
Urgency: Wait and watch
A dermatofibroma is a common skin growth that usually appears on the lower legs, but may appear anywhere on the body. These growths are benign (noncancerous). Dermatofibromas are most common in adults and are rarely found in children.
Symptoms include a hard, raised growth that is red, pink, ...
Melanoma is the most serious type of skin cancer. Often the first sign of melanoma is a change in the size, shape, color, or feel of a mole. Most melanomas have a black or black-blue area. Melanoma may also appear as a new mole. It may be black, abnormal, or "ugly looking."
Top Symptoms: brown-colored skin changes, atypical features of a facial bump, black-colored skin changes, growing facial lump, large facial lump
Symptoms that always occur with melanoma: atypical features of a facial bump
Urgency: Primary care doctor
A skin abscess is a large pocket of pus that has formed just beneath the skin. It is caused by bacteria getting under the skin, usually through a small cut or scratch, and beginning to multiply. The body fights the invasion with white blood cells, which kill some of the infected tissue but form pus within the cavity that remains.
Symptoms include a large, red, swollen, painful lump of pus anywhere on the body beneath the skin. There may be fever, chills, and body aches from the infection.
If not treated, there is the risk of an abscess enlarging, spreading, and causing serious illness.
Diagnosis is made through physical examination.
A small abscess may heal on its own, through the body's immune system. But some will need to be drained or lanced in a medical provider's office so that the pus can be cleaned out. Antibiotics are usually prescribed.
Keeping the skin clean, and using only clean clothes and towels, will help to make sure that the abscess does not recur.
Top Symptoms: rash with bumps or blisters, red rash, red skin bump larger than 1/2 cm in diameter, pus-filled rash, rash
Symptoms that always occur with skin abscess: rash with bumps or blisters
Urgency: Primary care doctor
Severe skin abscess
A skin abscess is an infection of the deeper skin that's typically due to bacteria seen on the skin. Recently, infections are more frequently caused by Staph. Aureus (puts the "staph" in "staph infections"). If the infection begins to spread, urgent treatment is required.
Top Symptoms: fatigue, fever, painful neck lump, marble-size neck lump, pink or red neck bump
Symptoms that always occur with severe skin abscess: pink or red neck bump, red bump
Urgency: Hospital emergency room
Basal cell carcinoma
Basal cell carcinoma is a slow-growing form of skin cancer. Skin cancer falls into two major groups: Non-melanoma and melanoma. Basal cell carcinoma is a type of non-melanoma skin cancer.
Top Symptoms: facial skin changes, pink or red facial bump, small facial lump, painless facial bump, growing facial lump
Urgency: Primary care doctor
Insect bite on the arm
Insect bites are a common occurrence. Despite the discomfort they cause, most bites are harmless and will resolve on their own.
Top Symptoms: swollen forearm, mild forearm pain, forearm bump, forearm redness, forearm itch
Symptoms that never occur with insect bite on the arm: fever, worsening forearm redness, severe forearm pain, high-pitched breathing, wheezing, racing heart beat
Warts are non-serious skin growths caused by a virus that infects the top layer of the skin. They are contagious.
Top Symptoms: skin-colored forearm bump, painless forearm lump, small forearm lump, scaly forearm bump
When to seek treatment for a hard lump on the forearm
Since the causes of forearm lumps are varied, it is important to make an appointment with your physician in order to get the proper diagnosis and treatment.
Depending on the cause of your symptoms, your physician may suggest the following.
- Surgery: Surgery is often the first option for removing both benign and malignant growths from the forearm and other areas of the body. Surgery for malignant growths is also often combined with other chemical treatments.
- Pain medication: Medications such as NSAIDs (non-steroidal anti-inflammatory agents) that help alleviate the pain associated with forearm lumps are often used to help treat this condition. Common NSAIDs include ibuprofen (Advil, Motrin) and naproxen (Aleve).
- Anti-inflammatory: Inflammatory causes of forearm lumps may be treated with various types of medications that target and decrease inflammation, such as immune system-suppressing drugs (immunosuppressants).
- Cancer treatment: If your forearm lump and associated symptoms are due to malignant cancer, your physician will discuss treatment options including surgery, radiation, or chemotherapy.
FAQs about hard forearm lump
Will the lump in my forearm go away on its own?
Depending on the cause, there is a possibility that the lump and the accompanying pain will go away on its own. If the forearm lump is a cyst or caused by environmental or inflammatory conditions, there is a good chance it will resolve on its own. However, if the forearm lump is a benign or malignant tumor, it will not resolve on its own and will require specific treatment.
Will the lump spread from one forearm to the other?
If the lump is red or multiple lumps appear on one arm, this is most likely an inflammatory etiology like panniculitis. These bumps may spread and affect the other arm or another limb in the first few weeks; however, they can be easily treated and often resolve on their own. Other causes of forearm lumps, on the other hand, usually do not spread from one forearm to the other.
Is the lump chronic or temporary?
A forearm lump may be temporary or chronic depending on the cause. A chronic forearm lump is more associated with benign or malignant growths, whereas temporary lumps are more associated with traumatic or inflammatory causes. However, arthritic nodules are a chronic, inflammatory etiology and need proper follow-up with a specialist, such as a rheumatologist.
How will the lump affect my daily activities?
A forearm lump can be very painful and uncomfortable, but those related to temporary etiologies should not affect you long-term. After a traumatic event, bed rest and limited activity with the affected forearm will help with recovery. A forearm lump associated with a benign or malignant growth may cause fatigue or unexplained weight loss, which may inhibit your energy to complete tasks. See your physician promptly if you feel like your symptoms are significantly affecting your life.
What can I do to prevent the development of forearm lumps?
It is very difficult to prevent the development of forearm lumps. The only situations in which the development of forearm lumps may be prevented are those related to environmental factors. There are several strategies you can employ to prevent bites from occurring, such as wearing protective clothing, using insect repellent, and going outside at times that mosquitoes are less active (during the day, after dawn and before dusk).
Questions your doctor may ask about hard forearm lump
- What color is the bump?
- Is your forearm bump painful to the touch?
- Any fever today or during the last week?
- Do you have a rash?
Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.
Dr. Gambrah-Lyles is a resident pediatrician at the Children's Hospital of Philadelphia. She is a graduate of the University of Pennsylvania Perelman School of Medicine (2019). She graduated cum laude and received her undergraduate degree in Biochemistry and Spanish from Washington University in St. Louis (2013). Her research explores the intersections between neurology, public health, and infectious disease. She has investigated nutrition and cerebral palsy in Botswana, and completed a year-long project in Brazil, researching growth and developmental outcomes of Zika virus infection in pediatric patients as a Doris Duke International Scholar. Dr. Gambrah-Lyles speaks four languages, loves staying active, and enjoys sharing her love for medicine through teaching and writing.