MRI diagnosis of bone marrow relapse in children with ALL
Diffuse marrow replacement in acute leukemia is well known, but there are few reports describing the MRI features of pediatric leukemic relapse. Our purpose was to describe the MRI appearance of pediatric leukemic relapse. A total of 53 consecutive children with a history of ALL were referred for musculoskeletal MRI from 1 January 1998 to 28 February 2007 at one center, and from 1 January 2000 to 2 May 2007 at a second center. From this group, 14 children seen at initial diagnosis of leukemia and 2 children who underwent MRI after therapy for relapse were excluded. The remaining 37 children, 8 with relapse and 29 in remission, were studied. Images of patients with relapse and in remission were reviewed for type and configuration of marrow infiltration; coexisting marrow alterations including osteonecrosis or stress reaction were also reviewed. All eight children with relapse demonstrated nodular lesions with well-defined margins. Coexisting osteonecrosis was present in three children (38%) and pathologic fracture in one. Among the 29 children in remission, 9 showed stress reaction/fracture, 14 showed osteonecrosis and 9 showed ill-defined nodules, and in 5 the marrow was completely normal. Well-defined nodules in all patients with leukemic relapse suggest that this appearance is characteristic and distinct from the published findings of diffuse marrow replacement in acute leukemia.