The differential diagnosis of single space-occupying lesions comprises multiple sclerosis (MS) in younger patients and primary or secondary brain tumour at any age. We describe a 70-year-old man with recurrent tumour-like intracerebral masses, which were diagnosed as tumefactive demyelination (TD). He presented with confusion, headache and hemineglect. Past medical history included coronary heart disease and atrial fibrillation. Magnetic resonance imaging (MRI) of the brain revealed a single right parieto-occipital lesion (Fig. 1a, d). Search for primary neoplasm (lymph nodes, blood cell analysis, computer tomography of the thorax and abdomen, and whole body deoxyglucose positron emission tomography) was negative. The cerebrospinal fluid including fluorescenceactivated cell sorter showed mild lymphocytic pleocytosis (27 cells/ll) and elevated protein (0.71 g/l), but no oligoclonal bands or tumour cells. Biopsy of the cerebral lesion showed foamy macrophages and focal perivascular lymphocytic cuffs, which are indicative of demyelination ( Fig. 1g-j). There was no evidence of a neoplasm. Following biopsy the patient rapidly improved to a course of oral dexamethasone starting with 12 mg per day. Six and 12 weeks later his MRI showed substantial regression of the lesion with residual non-space-occupying hyperintensity on T2-weighted MRI. Eight, 23 and 29 months later, the patient developed single symptomatic lesions again (representative images are shown in Fig. 1b, c, e and f). He again responded to oral dexamethasone, and clinical improvement was paralleled by a decrease of lesion volume and contrast enhancement on MRI. Repeated extensive search for a primary tumour was negative. Ten months after the initial presentation of TD the patient presented with adynamia, anaemia and leukopaenia. Bone marrow examination revealed myelodysplastic syndrome (MDS). Eleven months later the patient suffered from haematuria, which led to the diagnosis of renal cell carcinoma. He died 34 months after the first manifestation of TD due to metastatic renal cancer. Brain autopsy findings were similar to those of the biopsy. Again, there was no evidence of lymphoma or any other neoplastic process. Our final diagnosis was recurrent TD.Our patient developed four single tumour-like lesions at various sites of the brain over 3 years. There was no preceding viral infection or vaccination. From the initial appearance on MRI, central nervous system lymphoma was suggested. However, neither biopsy nor autopsy revealed tumour. Age, clinical course with recurrent single lesions and negative oligoclonal bands in our patient suggest that at least a subset of TD cases may represent a distinct entity rather than a manifestation of MS [1]. In our case the diagnosis of MS appears very unlikely. Based on the

No abstract