["Ghost and mimicry-tumor"--primary CNS lymphoma].

In recent years, the frequency of primary cerebral lymphoma (PCNSL) has increased, even among immunocompetent patients. In order to treat the disease optimally, early diagnosis is important. We present three patients with atypical courses of this disease and stress the importance of PCNSL in the differential diagnosis for optimal treatment. In a 75-year-old man, a space-occupying, radiopaque, enhancing CNS lesion disappeared completely after biopsy and short steroid therapy. One year later, the tumor recurred on the other side and again regressed after steroid therapy. The first biopsy showed signs of a papillary tumor, so a choroid plexus papilloma was suspected initially. A 57-year-old woman developed progressive bilateral hearing dysfunction. Lymphocytic pleocytosis led to a primary diagnosis of chronic lymphocytic meningitis. During the further course of disease, the patient developed multiple space-occupying cerebral lesions. Stereotactic biopsy revealed PCNSL. Despite combined chemo- and radiotherapy, a relapse occurred. A 49-year-old woman rapidly developed memory and concentration disturbances. Computed tomography revealed diffuse edema in both hemispheres and MRI detected severe, diffuse, white matter lesions. The CSF revealed lymphocytic pleocytosis including plasma cells. Herpes encephalitis and, after lack of clinical improvement and progression of the MRI changes, acute disseminated encephalomyelitis (ADEM) were suspected. Corticosteroid treatment was initiated. After enormous clinical improvement, a clinical relapse occurred and MRI detected bitemporal and singular space-occupying lesions in the corpus callosum and hypothalamus. Finally, open biopsy showed PCNSL. However, on examination of the treatment history of patient 1, the initial diagnosis must be revised; a PCNSL seems most probable. The phenomenon of tumor remission under steroid administration is rare. In patients 2 and 3, atypical clinical signs and symptoms delayed diagnosis of PCNSL. This tumor can mimic diverse neurological diseases and remit following corticosteroid treatment alone. In unclear cerebral disease, biopsy should be performed early for exact diagnosis and optimal treatment.