A SHINY LUMP THAT DEFORMS THE NAIL

Clinical presentation

Easy. Common.

The presence of a small, raised, soft, shiny lesion on the distal part of a finger should suggest a digital myxoid cyst, particularly when it is located close to the nail. And there is another clue that may be even more striking than the cyst itself: a longitudinal groove in the nail plate.

Digital myxoid cyst located close to the proximal nail fold. The longitudinal alteration of the nail plate secondary to involvement of the nail matrix can be seen.

A digital myxoid cyst, also known as a digital mucous cyst or digital myxoid pseudocyst, is a benign lesion that usually develops near the distal interphalangeal (DIP) joint and the nail unit.

It is usually less than 1 cm in diameter and presents as a small, smooth, rounded lesion, either skin-coloured or slightly translucent. It is generally asymptomatic, although it may become painful if inflamed or traumatized. Occasionally, it may spontaneously drain clear, viscous and sticky material.

Why does it develop?

It is more common from the sixth decade of life onwards and has a well-established association with osteoarthritis of the distal interphalangeal joint. In younger patients, repetitive trauma or repeated use of the affected finger may also contribute to its development.

In most cases, these are small ganglion cysts related to the underlying joint, particularly when degenerative joint changes are present. 

Schematic representation of a digital myxoid cyst related to the distal interphalangeal joint. The contents are gelatinous and rich in hyaluronic acid.

 

 The nail may provide the clue

This is probably one of the most interesting clinical features of a digital myxoid cyst.

When the lesion is located close to the proximal nail fold, it may compress the nail matrix. Because the matrix is responsible for producing the nail plate, sustained pressure on a small area may alter nail growth.

Cyst → pressure on the nail matrix → altered nail plate formation → longitudinal groove

The result may be a longitudinal depression or groove in the nail plate, producing true canaliform nail dystrophy. In some patients, this nail change may be more noticeable than the cyst itself.

Do we need additional investigations?

In most cases, no. Diagnosis is usually clinical, based on the combination of the characteristic morphology and location.

When the lesion is subungual, has an atypical appearance or there is diagnostic uncertainty, imaging may be useful and, occasionally, a biopsy may be required.

An X-ray may be useful when assessing for osteoarthritis or osteophytes of the distal interphalangeal joint, although it is not routinely required.

Does it always need treatment?

No. A small, asymptomatic cyst can simply be observed.

Treatment may be considered when there is pain, recurrent inflammation or drainage, thinning of the overlying skin, significant nail deformity, or functional or cosmetic impairment.

Treatment options

Option	Main advantage	Limitation
Observation	Appropriate for asymptomatic lesions. Avoids unnecessary procedures.	The cyst may persist or recur.
Drainage + compression therapy	Simple and minimally invasive. Sustained pressure may promote collapse of the cyst, fibrosis and reduce refilling after drainage.	Recurrence may occur, and the available evidence is more limited than for surgery.
Cryotherapy	A relatively simple outpatient procedure.	Risk of recurrence and local tissue injury.
Sclerotherapy	A non-surgical alternative with a good response rate.	May cause pain, inflammation and recurrence.
Surgery	It has the highest cure rate; systematic reviews report rates approaching 95%.	Risk of scarring, stiffness, pain or infection.

The main disadvantage of conservative procedures is recurrence. Surgery has the highest cure rate, particularly when the lesion is adequately treated and, when appropriate, associated joint changes are addressed.

Take-home message

When you see a small, shiny or translucent lump close to a distal interphalangeal joint, particularly in a patient with osteoarthritis, consider a digital myxoid cyst. If there is also a longitudinal groove or canaliform nail dystrophy, the nail itself may be pointing to the underlying problem.

References and further reading

British Association of Dermatologists. Digital myxoid cysts. Updated September 2024. British Association of Dermatologists .

Jabbour S, Kechichian E, Haber R, Tomb R, Nasr M. Management of digital mucous cysts: a systematic review and treatment algorithm. International Journal of Dermatology. 2017;56:701-708. PubMed .

Laulan J, Chammas M. Digital mucous cyst. Hand Surgery & Rehabilitation. 2024. PubMed .

DermNet NZ. Digital myxoid pseudocyst. DermNet .