Utility of whole-body bone scintigraphy and SPECT/CT for the differential diagnosis of Ewing sarcomas /PNET and small cell osteosarcomas before neoadjuvant therapysition:relative;top:1.5000pt;mso-text-raise:-1.5000pt;" >Ewing sarcoma /PNET; Small cell osteosarcoma;Bone scintigraphy (BS); SPECT/CT;Dignosis

Objectives: Microscopically, the Ewing sarcomas /PNET and small cell osteosarcomas shared similar histology with small round cells and spindly cells arranged in diffuse sheets and pre-surgical pathological differential diagnosis is challenging in the absence of the osteogenesis on the core needle biopsy. This study was performed to evaluate the utility of whole-body bone scintigraphy (BS) and SPECT/CT for the differential diagnosis before pre-surgical neoadjuvant therapy.

Methods: We retrospective analyzed baseline whole-body bone scintigraphy (BS) and core needle biopsy results of 85 patients with pathologically diagnosis of Ewing sarcoma /PNET and small cell osteosarcoma from 2009 to 2017. The post-operative pathology was served as gold standard. Results: There were 68 patients with Ewing sarcoma/PNET and 17 patients with small cell osteosarcoma (51 males and 34 females, age range from 2 to 58 years). The tumors involved limbs, axial skeleton and flat bones. For the diagnosis for small cell osteosarcoma, the BS was correct in 76.5 % (13/17) patients as compared with post-operative surgical pathology. Core needle biopsy was correct in 58.8 % (10/17) patients and 5 of the 17 patients were misdiagnosed as Ewing sarcoma /PNET and 2 patients were diagnosed as osteosarcom. When core-needle biopsy was wrong, 6 patients diagnosed correctly by BS and SPECT/CT. For the diagnosis of Ewing sarcoma /PNET, BS was correct in 82.4% (56/68) patients, and the core needle biopsy was correct in 89.7 %(61/68) patients and 7 of the 68 patients were diagnosed as small cell malignant tumors. When core-needle biopsy was ambiguous, 5 patients diagnosed correctly by BS and SPECT/CT.Conclusions: BS and SPECT/CT can supplement core-needle biopsy for the differential diagnosis of Ewing sarcomas /PNET and small cell osteosarcomas before neoadjuvant therapy and surgery.Key words Ewing sarcoma /PNET; Small cell osteosarcoma; Bone scintigraphy (BS); SPECT/CT; Dignosis