Tendon sheath cysts are common masses in the wrist and hand. Tendon sheath cysts, which are not really tumors but can be classified as tumor-like diseases or tumor-like lesions, are common masses in the hand, mainly in the synovial membrane, tendon sheaths, and tendons, and chronic injury increases synovial fluid in the synovial cavity and forms cystic herniation or connective tissue mucosal degeneration as an important cause of morbidity. Tendon sheath cysts can occur at any age, but they are more common in young and middle-aged people, and are more common in women than men. Tendon sheath cysts can be manifested as follows: 1, the most common tendon sheath cysts are on the dorsal side of the wrist, round, oval, smooth surface, tough texture, and when pressed, the mass can be seen moving freely under the skin, and some can be painful; 2, the next most common site is the radial side of the wrist palm (i.e., the pulse); there are also occurring in the distal end of the palm or the proximal end of the fingers, such people are often on the flexor tendon sheath, such as the size of a grain of rice, hard as bone. They are filled with colorless or slightly yellowish transparent jelly-like mucus. Cysts can appear suddenly or can grow slowly from small to large. It can disappear on its own after an external force or without significant external force, and reappear later. Doctor’s tip: Tendon sheath cysts can cause soreness and pain, which may affect the normal activities of the hands and feet, and severe tendon sheath cysts may also compress the median nerve of the patient and induce carpal tunnel syndrome, so tendon sheath cysts must be treated promptly.