Granulocytic sarcoma of the knee and the spine as aleukemic relapse of acute myeloid leukemia in a child.

Granulocytic sarcoma is a very rare disease in childhood, which may precede the clinical manifestations of acute myeloid leukemia or may occur as a relapse of a nonleukemic acute myeloid leukemia. It is a malignant, solid tumor consisting of myeloblasts or immature myeloid cells occurring in extramedullary sites. We report interesting magnetic resonance images of a nonleukemic relapse of acute myeloid leukemia in a child presenting as a granulocytic sarcoma unusually localized to the knee and spine.