What is a granuloma?

A granuloma is a tiny cluster of white blood cells and other tissue that can be found in the lungs, head, skin or other parts of the body in some people. Granulomas are not cancerous. They form as a reaction to infections, inflammation, irritants or foreign objects.

What are the types of granulomas?

Foreign body granulomas

This type of granuloma develops when the body's immune system reacts to an object or irritant that penetrates the skin, eye or body. They can form in reaction to:

• foreign objects such as splinters
• bee stings and spider bites where parts of the insect's body are left behind
• substances that irritate the person, including red tattoo ink and the silica in talcum powder
• injections, including corticosteroids and dermal fillers, such as collagen
• surgical stitches

Skin granulomas

Several types of granuloma can affect the skin. The most common is granuloma annulare, a harmless skin condition that causes raised pink or flesh-coloured bumps under the skin. The bumps are usually found over bony areas, like the elbow, and may have a distinctive ring shape. They often affect hands and arms, but can also affect legs, feet, trunk or face.

What causes granulomas?

Granulomas form when immune cells clump together and create tiny nodules at the site of the infection or inflammation.

A granuloma is the body's way:

• to contain an area of bacterial, viral or fungal infection so it can try to keep it from spreading; or
• to isolate irritants or foreign objects

Granulomas most frequently form in the lungs, but can also be found in the liver, the eye or under the skin. They can be felt as a lump or can show up on x-rays and during other investigations.

Granulomas caused by other conditions

Granulomas can be part of conditions such as:

• sarcoidosis — a non-infectious disease that can cause multiple granulomas in different parts of the body, but especially in the lungs
• chronic granulomatous disease — an inherited immunodeficiency condition that starts in childhood and leads to recurring bacterial and fungal infections
• Crohn's disease and inflammatory bowel disease
• rheumatoid arthritis

How are granulomas diagnosed?

Your doctor or specialist will take a medical history and examine you if they suspect you might have granulomas. They may ask for tests such as a blood test, x-rays or CT scans, genetic tests or a needle biopsy.

Scans may show numerous minute granulomas in an organ such as the lungs. These can help diagnose the underlying cause.

With skin granulomas, your doctor may only need to do a physical examination to confirm a diagnosis.

How are granulomas treated?

Some people with a granuloma need treatment, buts others may not. It depends on the type of granuloma.

For example, people with chronic granulomatous disease may be given antibiotics and other treatments to try to prevent further infections. Find out more about chronic granulomatous disease treatment here.

More than half of all people affected by sarcoidosis recover without treatment within 3 years. Learn here about sarcoidosis treatment.

Most forms of granuloma annulare get better without treatment. Sometimes, however, people want treatment for cosmetic reasons and may be given corticosteroids or phototherapy. Find out more about granuloma annulare treatment here.

Are granulomas cancerous?

Although granulomas may appear cancerous, they are not — they are benign.

Occasionally, however, granulomas are found in people who also have particular cancers, such as skin lymphomas. So it is important to consult a doctor if you notice persistent lumps on your skin or have other symptoms of illness.