A 4-year-old boy presenting with a painless scalp tumor was initially planned to undergo invasive biopsy. The MR findings of the scalp tumor itself were nonspecific; however, those of the bone marrow showed low intensities on T1 and T2 weighted images, and mild high intensity on fat saturated T2 weighted image. Diffusion-weighted image also showed high intensity with a low ADC value. Based on these MR findings, we performed bone marrow aspiration prior to biopsy which confirmed a diagnosis of acute lymphoblastic leukemia. In children with a soft tissue tumor or a tumor-like condition without any clinical symptoms or abnormalities on blood tests, we should consistently be aware of the possibility of acute lymphoblastic leukemia in the differential diagnosis. MR may provide useful information not only of a local lesion but also of the bone marrow providing clues to the diagnosis.
