Abstract
We clinicopathologically analyzed 12 cases who were initially diagnosed as malignant brain tumor, but were
difficult to diagnose after surgery. Finally, 4 cases were diagnosed as malignant brain tumors, and 8 as nonneoplastic
disease. By unusual clinical course, four patients were changed their preoperative diagnosis to nonneoplstic
disease and surgery was performed to rule out tumor. Craniotomies were performed in 9cases, and
stereotactic biopsies in 3. In five cases, inflammatory changes were seen and we diagnosed these cases as
multiple sclerosis, vasculitis or encephalitis. In two cases, pathological findings supported cerebral infarction.
There were no pathological findings in four cases, The reasons that surgical specimen did not give diagnostic
yield were that they were too small or obtained from unappropriate resion. We also found malignant lymphoma,
（especially intravascular lymphoma）is the most difficult to be distinguished from other disease such as inflammatory
processes without histopathological examintaion. There has been no patient whose diagnosis changed
again due to clinical course after treatments. These results suggested that if surgical specimen had sufficient
pathological yields, they bring us some clues to decide clinical diagnosis and exact treatment strategy.
