A patient developed a rapidly progressive and extensive periprosthetic osteolysis after a cemented total hip arthroplasty for postradiation necrosis of pelvic bone and femoral head. Malignant tumor is one of the causes of periprosthetic bone loss. The biopsy confirmed the malignant fibrous histiocytoma (MFH). However, majority of periprosthetic bone loss is due to wear debris induced osteolysis. Usually, wear debris induced periprosthetic osteolysis is developed later and the progression is much slower than there of malignant tumor. Also wear debris induced osteolysis is confirmed by chronic inflammation with macrophages containing wear particles. When there is a rapidly progressive and extensive osteolysis a prosthesis following hip replacement arthroplasty, the physician should suspect the possibility of malignant tumor.