OBJECTIVETo study the difference in pathologic diagnostic accuracy among different histologic subtypes of osteosarcoma and different methods of preoperative biopsy, and the influence of diagnostic accuracy on prognosis of osteosarcoma.

METHODSThe preoperative biopsies, complete clinical, radiological and pathological data of 347 pathologically confirmed osteosarcomas were evaluated. According to the Pathological Diagnostic and Technical Specifications, the accuracy of preoperative biopsies was divided into 6 grades. 1: definite diagnosis, 2: basically definite diagnosis, 3: significant diagnosis, 4: descriptive diagnosis, 5:inadequate sampling, 6:misdiagnosis. 1 to 3 were defined as successful diagnosis,while 4 to 6 were defined as unsuccessful diagnosis.

RESULTSOf the 347 biopsies, 252 were CT-guided needle biopsies by the radiologists, and 95 were core-needle biopsies by orthopedic surgeons without CT-guidance. The latter showed a higher overall biopsy success rate (97.9%) in all osteosarcomas. Biopsies by surgeons showed a higher biopsy success rate (95.4%) in conventional osteosarcoma, but lower success rate in telangiectatic (55.6%) and low-grade central osteosarcomas (63.7%). The accuracy of pathologic diagnosis of preoperative biopsy was related to patients' age, serum AKP level, imaging diagnosis, method of biopsy and the subtype of osteosarcoma. Comparing the groups with successful and unsuccessful diagnosis, there were significant differences in recurrence rate and mortality after operation (P<0.01).

CONCLUSIONSThe accuracy of pathologic diagnosis of preoperative biopsy are related to recurrence rate and mortality after operation. Biopsy by orthopedic surgeons without CT-guidance is reliable and safe, followed by primary diagnosis at frozen section and final diagnosis by routine pathologic sections for osteosarcomas located in the long bones of the extremities. Close integration of the preoperative pathologic diagnosis with clinical and radiological data will improve the accuracy of diagnosis.