Metastatic Malignant Lymphoma Mimicking Cerebral Toxoplasmosis with the "Target Sign"

We herein report the case of a 60-year-old man with a "target sign" in the left frontal lobe on magnetic resonance imaging (MRI), which is thought to be a specific sign of cerebral toxoplasmosis. 18F-fluorodeoxyglucose-positron emission tomography showed no increased uptake, and 201Tl-single photon emission computed tomography showed the focal uptake in the left frontal lesion. On a brain biopsy, the patient was given a definitive diagnosis of brain metastasis from diffuse large B-cell lymphoma, and cerebral toxoplasmosis was excluded. In the present case, multilayer intensities on MRI may reflect the fast-growing nature of this tumor.