hygroma

A hygroma is a benign, fluid-filled swelling that arises from a bursa or the synovial lining of a joint or tendon sheath. The term is often used interchangeably with ganglion cyst, especially when the lesion is near a joint or tendon. Hygromas most commonly occur on the dorsal wrist, but can also appear around the knee, ankle, elbow, or other joints, and they are described in animals as well.

Etiology and pathology are not always clear, but hygromas are thought to result from herniation or degeneration of synovial tissue with accumulation of viscous fluid. Repetitive mechanical stress, degenerative joint disease, or inflammatory conditions may predispose to their formation. The cyst is typically well circumscribed and movable beneath the skin.

Clinical features include a soft to firm lump that is usually painless but may cause discomfort if it enlarges or compresses nearby structures. The size may fluctuate. Transillumination can occur. Diagnosis is based on history and examination, with imaging such as ultrasound or MRI used to confirm a cystic lesion and exclude other masses. Aspiration of the fluid can aid diagnosis, though it is not always definitive. Radiographs may help assess underlying joint pathology.

Management ranges from observation to intervention. Asymptomatic hygromas may be left alone. Symptomatic lesions or those causing cosmetic concerns may be treated with aspiration, with recurrence common, or with surgical excision that removes the cyst wall and, when feasible, part of the adjacent joint capsule or bursa. Prognosis is generally favorable after complete excision, though recurrence can occur if the cyst wall persists.