Radiological characteristics and predisposing factors of venous tumor thrombus in pelvic osteosarcoma: A mono‐institutional retrospective study of 115 cases

BACKGROUND: Venous tumor thrombus (VTT) in pelvic osteosarcoma has been regarded as a rare oncological condition and few literatures investigated this issue. METHODS: We retrospectively reviewed 115 cases of pelvic osteosarcoma treated in our center from 2006 to 2016. Diagnosis of VTTs was made based on histo‐pathological findings. We summarized the radiological manifestations of VTTs on CT, MRI, and PET/CT. We also compared the demographical, oncological, and radiological data between cases with or without VTTs to identify its predisposing factors. RESULTS: Seventeen cases (14.8%) were diagnosed with VTT. Manifestations of VTTs on CT included increased caliber (64.7%), calcification (47.1%), low density on plain scan (100%), filling defect (100%), and streak‐like enhancement (35.7%) on contrast enhancement. On MRI, the VTTs could be hypo‐ or iso‐intense on T1WI (100%), hyperintense on T2WI (100%), and filling defect on contrast enhancement (100%). PET/CT showed high metabolic activity of the VTTs. The ranges of the VTTs included unilateral external iliac vein (EIV) (two cases), unilateral internal iliac vein (IIV) (one case), unilateral common iliac vein (CIV) and IIV (five cases), unilateral CIV + EIV (two cases), inferior vena cava (IVC) and unilateral CIV + EIV (one case), IVC and unilateral CIV + IIV (four cases), IVC and bilateral CIVs + IIVs (two cases). Multivariate analysis indicated that chondroblastic subtype and involvement of L5/S1 intervertebral foramen might predispose to VTTs. CONCLUSION: The incidence of VTTs in pelvic osteosarcoma was 14.8%. Comprehensive radiological studies help preoperative diagnosis of VTTs. Predisposing factors included chondroblasic subtype and involvement of L5/S1 intervertebral foramen.