MR features of an intracerebellar chloroma

Granulocytic sarcoma (chloroma) is a rare tumor almost always associated with leukemia. Intraaxial brain lesions are rare, and can mimic infection or primary neoplasm. This intracerebellar chloroma arose after autologous bone marrow transplantation in a 29-year-old woman with leukemia. On T1-weighted MR images, the lesion was isointense with gray matter, and enhanced homogeneously. On T2-weighted and proton density-weighted MR sequences, the center was isointense with gray matter and the periphery was isointense with white matter. The lesion's tendency to remain isointense on sequences with long repetition times is presumably attributable to the presence of myeloperoxidase.