If there is a hard lump on the leg, it should be judged according to the specific part of the hard lump. If it is a hard lump in the groin area, it may be an enlarged inguinal lymph node, inflammation in the lower extremity may be caused by dengue, or it may be a lymphoma. If it is a hard lump in the thigh or calf area, it may be a subcutaneous lipoma, which is a benign tumor due to the proliferation of fatty tissue under the skin, with clear borders. If a hard mass appears under the skin in a short period of time at the front of the calf, it is considered to be a bone related malignant tumor, such as osteosarcoma, which is more malignant, grows rapidly, hard to touch, and adheres to the surrounding tissues, and can be treated surgically in the early stage, but the mortality rate is higher in the late stage.