BACKGROUND: Since the introduction of megavoltage radiation therapy @entity1161 has become a rare event and may be easily mistaken for bone @entity3 . A case of @entity1161 is reported and diagnostic features are discussed. CASE REPORT: A 70 year-old female @entity1 underwent rectum resection for rectum @entity5 and was given standard adjuvant therapy consisting of irradiation of the @entity5 site and lymph nodes in the pelvis with 18 MeV photons, boxfield technique up to 50.4 Gy and chemotherapy with @entity1487 . Eight months later she complained of severe @entity615 . Plain radiographs and CT revealed @entity690 in the @entity2720 and os sacrum which appeared as circumscript areas of signal loss in MRI (T1-weighted sequence). A soft tissue mass was not detected. CT-guided biopsy excluded bone @entity3 . CONCLUSION: Characteristic features of @entity1161 are spongiosa destructions initially in weight-bearing bones within the radiation field, namely the @entity2720 , and the lack of pathologic soft tissue mass. False treatment, i.e. radiation for bone @entity3 , should be avoidable.

[Radiation-induced osteonecrosis of the pelvic bones vs. bone XXXX --a difficult differential diagnosis].

@entity1 :: ('9606', 'Species') :: ['patient'] @entity1161 :: ('MESH:D011832', 'Disease') :: ['radiation osteitis'] @entity5 :: ('MESH:D009369', 'Disease') :: ['tumor', 'cancer'] @entity615 :: ('MESH:D001416', 'Disease') :: ['lower back pain'] @entity3 :: ('MESH:D009362', 'Disease') :: ['metastases'] @entity690 :: ('MESH:D030981', 'Disease') :: ['osteolytic lesions'] @entity2720 :: ('MESH:D007592', 'Disease') :: ['ileosacral joints'] @entity1487 :: ('MESH:D005472', 'Chemical') :: ['5-FU']
@entity3 :: (MESH:D009362,Disease) :: ['metastases']
