A hard lump on the thumb may be associated with tendon sheath cysts, gouty stones, common warts, and calluses. 1. Tendon sheath cyst: a cystic swelling in the tendon sheath of the joint due to various reasons. In addition to localized swelling, there may be pressure and pain discomfort, ultrasound examination can be clearly diagnosed. 2. Gout stone: is due to the deposition of uric acid crystals and the formation of a mass, acute attack, there will be obvious local redness, swelling and hot pain, local puncture can be seen in the uric acid crystals, renal function tests can be found in the uric acid increase. 3. common warts: a skin disease caused by infection with human papilloma virus, the disease can be transmitted through close contact or indirect contact, in the clinic is mainly manifested as a flat papule, can also be presented as a rough surface of the round bumps. 4. callus: is due to prolonged extrusion or friction and lead to local skin keratosis, palm and metatarsal force parts. Due to the many causes, the specific situation needs to ask the doctor for an interview, and under the guidance of the doctor for treatment.