A 30-year-old man with thalassemia major was referred with headache. Neurological examination revealed no abnormalities and a diagnosis of ‘tension headache’ was made. An analgesic and an antidepressant were prescribed. After taking these medications for 3 months, his headache hadn’t improved so cranial magnetic resonance imaging (MRI) was done. This revealed a mass in the interhemispheric fissure measuring 4 × 5 × 11·5 cm (Image). A biopsy of the lesion showed extramedullary haemopoiesis. The mass was considered unsuitable for surgery or radiotherapy. Hydroxycarbamide treatment in a dose of 1000 mg/day and hypertransfusion therapy were initiated.