Ask the expert

Hard lump in my upper arm

1 March 2021

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 your lump has developed, it’s unlikely to be scar tissue.

A lump like the one you describe could be:

Lymph gland

The location of your lump near the lymph glands in your armpit suggests that this could be a raised lymph gland, caused by an infection.

Epidermal cyst

These affect the epidermis layer of the skin and are made up of keratin and fat. They are generally found on the face, neck, shoulders, chest and upper body and can be triggered by acne or mild injuries to the skin. Look for a slowly developing cyst with a rounded appearance, often no larger than 5cms in size. Key characteristics of epidermal cysts:

  • Usually not painful unless they're burst or become infected
  • Usually non-cancerous
  • These cysts tend to disappear without treatment but if need be, can be treated with antibiotics, steroid injections or excision (surgical removal).

Pilar cyst

These are keratin filled cysts, originating from the outer hair root sheath/hair follicle. Look for these on the scalp and around hairline areas. 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.


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. Key characteristics of lipomas:

  • Usually harmless
  • They can appear on various parts of the body but are less common around the scalp and neck
  • If these lumps grow, become larger or firmer to touch they should be investigated to eliminate the presence of cancerous cells
  • These can often be left, but if treatment is necessary can be excised or removed by cryotherapy (applying extreme cold to the area).


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.


This is a very rare type of cancer that often surrounds body structures and organs. A cure is readily achievable if an early diagnosis is made.

Treatment for your lump will depend on diagnosis, so speak to your GP, who may investigate further with a biopsy or ultrasound.


NHS 2021, Skin cyst.  (Accessed 01 March 2021)

NHS 2021, Lumps. (Accessed 01 March 2021)

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