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What is a Cyst?

By Nabta Team
Nabta Health

Cysts are sac-like pockets of tissue containing fluid, pus or gas - think “water balloons”. They are common and can grow anywhere inside the body or under the skin.

There are many different types of cysts, and most are benign (i.e. non-cancerous) although they may be painful depending where on the body they occur.

Types of Cyst

There are many different types of cyst. Some examples are as follows:

  • Epidermoid cysts - small, benign cysts caused by a buildup of keratin under the skin that usually appear on the face, head, neck, back or genitals.
  • Sebaceous cysts - benign cysts caused by damaged or blocked glands that occur under the skin on the face, neck and or torso.
  • Breast cysts - lumps occurring on the breast or under the armpit that could be benign or cancerous so it’s always worth getting these checked out if you discover a new one. Check out our tips on conducting breast exams here.
  • Ganglions - round, fluid-filled lumps of tissue usually caused by trauma or damage to the tendons or joints. Commonly found in the hands, wrists, ankles and feet.
  • Pilonidal cysts - small holes that appear in the cleft at the top of the buttocks and may fill with fluid or pus if infected.
  • Ovarian cysts - fluid-filled sacs that develop on one or both ovaries.
  • Chalazias - small, usually painless lump caused by a blocked oil gland occurring on the upper or lower eyelid.
  • Popliteal cysts - fluid-filled swellings that appear as lumps on the back of the knee and can cause stiffness and restricted movement.
  • Cystic acne - the most painful type of acne caused by bacteria, oil and dry skin cells blocking pores on the face, chest, neck, back and arms.
  • Ingrown hair cysts - pimple-like bumps under the skin that form when a hair grows sideways or downwards instead of out.
  • Pilar cysts - flesh-coloured, benign bumps under the skin formed by protein buildup in a hair follicle. Usually located on the scalp.
  • Mucous cysts - fluid-filled swelling on the lip or mouth caused by trauma such as lip biting or piercings.


  • “What’s causing this cyst?”, Healthline, Medically reviewed by Stacy Sampson, DO on August 11, 2017 — Written by Amanda Delgago