Abstract： Background Pathological fractures signify a potentially more aggressive subset of the original disease with higher misdiagnosis rates and inferior oncologic results.The purpose of the present study was to explore the clinical features of neoplastic pathological fracture in extremities.Methods From August 2002 to December 2010,a consecutive series of 139 patients suffering neoplastic pathological fracture were recruited,including 79 males and 60 females with a mean age of 31.3 years.Fractures were classified into five groups:tumor-like lesions (55),benign bone tumors (13),giant cell tumors (7),primary malignant bone tumors (28),and metastatic bone tumors (36).Based on their inducing forces,pathologic fractures were classified into four grades:spontaneous fracture,functional fracture,minor injury,and traumatic injury.Patients' age,fracture site,histological diagnoses,fracture forces,prodromes,and misdiagnosis were well reviewed.Kruskal-Wallis and x2 tests were used to compare forces and prodromes within different types of bone tumors.Results The highest pathologic fracture morbidity was 32.3％ (45/139),which lay in the 11-20 year group,and 86.1％of metastatic tumors occurred in the 50-80 year group.The common sites of fractures were femur,humerus,and tibia.The fracture forces in benign bone tumors and tumor-like lesions are the strongest,followed by metastatic tumors and primary malignant bone tumors (Hc=80.980,P=0.000).Sixty-seven patients (48.2％) had local prodromes before pathologic fracture.The incidence rates of prodromes between primary malignant tumors and metastatic bone tumors had no significant difference (P=0.146),but they were all obviously higher than that of benign bone tumors and tumor-like lesions.Twenty patients experienced misdiagnosis.Conclusion Minor injury forces and local prodromes are clinical features of neoplastic pathologic fractures and they are also the critical factor avoiding misdiagnoses.