A hard lump at the base of the thigh that hurts when pressed may be caused by sebaceous cysts, lymphadenitis at the base of the leg, boils and other causes. 1. Sebaceous cysts: cysts formed when the sebaceous gland ducts are blocked and sebum is not excreted. If there is a secondary infection, a hard lump that hurts when pressed will also appear, and it usually requires anti-infective treatment such as the use of antibiotics, followed by surgical excision. 2. Lymphadenitis at the root of the leg: due to inflammation and infection in the leg, the lymph nodes at the root of the leg will become enlarged, and a hard lump at the root of the thigh will appear and hurt when pressed, it is recommended to go to the hospital for examination to find out the cause of the problem. 3. Boils: mainly due to the inflammation of individual hair follicles caused by inflammatory swelling of the surrounding soft tissues, in the early stage there will be redness, swelling, heat and pain, can also cause a hard lump at the base of the thighs when pressed, the phenomenon of pain. It is recommended to go to the hospital for examination to clarify the cause of the disease and timely symptomatic treatment.