Background: Diffuse marrow replacement in acute leukemia is well known, but there are few reports describing the MRI features of pediatric leukemic relapse.
Objective: Our purpose was to describe the MRI appearance of pediatric leukemic relapse.
Materials and methods: 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.
Results: 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.
Conclusion: 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.