What are Mucous Cysts?
A mucous cyst is a benign (non-cancerous) fluid filled cyst arising from the DIP joint. It often presents with a swelling close to the bottom of the fingernail or back of the finger or can cause ridging of the nail. In some instances, the skin can become thin and breakdown and leak a clear fluid. It typically occurs in patients over 50 years of age and can be associated with early arthritis of the knuckle. It is important not to try and pick the skin or pop the cyst with a needle (or any non-sterile instrument) as this can introduce infection into the joint which can need urgent surgery.
What is the treatment for mucous cysts?
These cysts can sometimes resolve spontaneously and will only require treatment if they cause ongoing pain, skin breakdown or are unsightly to the patient.
Surgery can be performed to stop the fluid filling the cyst which allows the swelling to resolve. Treatment can usually be performed under local anaesthetic to clean out the knuckle which is the source of fluid that feeds the cyst. In some rare instances, the cyst needs to be cut out and skin may need to be rotated from the back of the finger to cover the defect.
What are the risks of surgery
- Recurrence – Chances of the cyst recurring in the same finger following surgery is less than 2% (1). Needle aspiration is not recommended as studies have shown a high risk of recurrence of between 30% and 100%.
- Pain – If the cause of pain is due to arthritis in the knuckle, this may persist even after the cyst is removed. If DIP joint (knuckle) arthritis is the main problem, the choice of initial surgery may be different.
- Infection – The risk of infection following surgical cyst removal is low (<1%).
- Nail deformity – Any pre-existing nail deformity usually resolves after pressure from the cyst is relieved. However, surgery itself can uncommonly cause permanent nail damage.
