Lump on arm

Emma Cronin, registered nurse and midwife

Possible causes of lumps in the arms

21 January 2025

Most lumps are harmless and can be a variety of things, from a simple cyst to rarely something more serious. They can be caused by infections, inflammation, disease or trauma.

It’s important to have all the information to make a diagnosis. So, for example, if there has been no injury near the area where a lump has developed, it’s unlikely to be scar tissue.

Hard lumps on the upper arms could be caused by:

Lymph gland

The location of a lump near the lymph glands in your armpit suggests that this could be a raised lymph gland, caused by an infection.1 As swollen lymph glands are usually caused by an underlying infection, you might expect to see a decrease in swelling in 1-2 weeks.

Treatment options could include:

  • plenty of rest,
  • keeping hydrated,
  • painkillers, if you are experiencing discomfort.

If the swelling persists or it gets bigger, then there may be another cause so it would be advisable that you see your GP.

Epidermal cyst

These affect the epidermis layer of the skin (top layer) and are nodules filled with keratin.2 They are generally found on the face, neck, shoulders, chest, and upper body and usually occur without a cause.

Epidermoid cysts pop up for no particular reason: there is nothing you can do to prevent them. They are not related to cleanliness, nor will exfoliating stop them occurring.3

Look for a slowly developing cyst with a rounded appearance, often no larger than 5cms in size. Key characteristics of epidermal cysts include:

  • Usually not painful unless they're burst or become infected.
  • Usually non-cancerous.
  • These cysts tend to disappear without treatment.

Treatment options

If advised by a health professional, epidermal cysts can be treated with:

  • Antibiotics
  • Steroid injections
  • Excision (surgical removal)

Pilar cyst

Like epidermal cysts, these are also keratin-filled, originating from the outer hair root sheath/hair follicle. Look for these on the scalp and around hairline areas.4 They can be difficult to distinguish from epidermal cysts in appearance and size.

Key characteristics of pilar cysts: 

  • They run in families.
  • They're non-cancerous.
  • Often disappear without treatment.
  • Can be treated if needed with antibiotics (if infected) or excision surgery.

They occur in less than 10 percent of the population but are the most common type of skin cyst.4

Lipoma

These can grow under the skin, as well as internally within the body. Look for a soft, fatty, moveable lump that grows slowly up to a couple of centimetres in size.5

Key characteristics of lipomas:

  • Usually harmless.
  • They can appear anywhere on the body.
  • If these lumps grow, become larger or firmer to touch they should be investigated by a health professional to eliminate the presence of cancerous cells.

Treatment

Lipomas do not tend to require removal as they are often harmless. If you are concerned or have noticed a change in a lump anywhere on your body, you should consult your GP who can help diagnose and provide you with removal options.

Fibroma

This is a benign tumour that can occur within any organ. Rarely do fibromas become cancerous and they may not need to be removed. Surgery is one option for managing them.

Sarcoma

This is a very rare type of cancer that often surrounds body structures and organs. Treatment for your lump will depend on diagnosis, so speak to your GP, who may investigate further with a biopsy or ultrasound.

>Find out more about soft tissue sarcomas

If you are concerned about any lumps on your body then speak with your GP to help diagnosis and get peace of mind. Any lump that is also increasing in size, discomfort or appearance, or has not resolved within 2 weeks, should be reviewed by a GP, where investigations such as biopsies and scans may be recommended.

References

  1. Swollen glands - NHS
  2. Epidermal cyst - NIH
  3. What causes epidermoid and pilar cysts? – Patient Info
  4. Pilar Cyst - NIH
  5. Lipoma - NHS



Discover AXA Health insurance