A rare case of tumor-mimicking primary angiitis of the central nervous system.

Primary angiitis of the central nervous system (PACNS) is a rare, but severe vascular disease. The present study reports the case of a 42-year-old male who developed PACNS. Magnetic resonance imaging (MRI) scans initially led to a misleading diagnosis of malignant glioma, and surgery was performed. The mass was resected, and a pathological examination confirmed a cerebral vasculitis. Single therapy with high doses of steroid did not improve the patient's condition, while a subsequent lesion appeared on the opposite side one year later. Combined therapy with methylprednisone and cyclophosphamide resulted in a great improvement for the patient. No relapse occurred during one year's follow-up. Although a tumor-mimicking PACNS has no established imaging features, a diagnosis of tumor-mimicking PACNS should be suspected when the MRI reveals inappropriate presentations of a tumor. Greater awareness of this potential manifestation of PACNS may facilitate more prompt diagnosis and treatment.