A myxoid cyst (also known as a digital mucous cyst or pseudocyst) is a ganglion cyst arising from the distal interphalangeal (DIP) joint of the finger or thumb (or, less commonly, toe). The cysts are believed to form from degeneration of connective tissue and are associated with osteoarthritic joints. Although the exact etiology for myxoid cysts and ganglion cysts is unknown, it is likely that a small tear forms in a joint capsule or tendon sheath, allowing extravasation of synovial fluid into the adjacent tissue. When the fluid reacts with local tissue, it becomes more gelatinous and a cyst wall forms.

Compared with ganglion cysts, which are mostly found in people between the ages of 15 and 40 years, myxoid cysts are more prevalent in women between the ages of 40 and 70 years.

They are typically 3-10 mm in size, most commonly affect the second and third digits, and are seen more often in women than men. The most common presentation is a solitary myxoid cyst, but 2-3 cysts can be seen in some patients.

Myxoid cysts are benign, but patients may seek treatment if they become unsightly, cumbersome, or painful. A number of treatment options are available.

Myxoid cysts are uncommon in children but have been reported in patients as young as 12 years.