Tumefactive primary central nervous system vasculitis mimicking a brain metastasis in a patient with kidney cancer

A 71-year-old male patient with papillary renal cell carcinoma (RCC) presented with confusion, right hemiparesis, and aphasia. A Head computed tomography (CT) scan ([Figure 1]) demonstrated a hyperdense swollen cortex on the left side, patent left middle cerebral artery (MCA), and abnormal perfusion. A brain magnetic resonance imaging (MRI) scan and a positron-emission tomography–computed tomography (PET-CT) scan ([Figure 1]) at one month of follow-up showed a round lesion with low fluorodeoxyglucose (FDG) uptake with enhancement and laminar cortical necrosis. The differentials included brain metastasis. After the surgery, the pathology ([Figure 2]) favored vasculitis. This pseudotumoral presentation of central nervous system (CNS) vasculitis is always challenging,[1] especially in cancer patients.[2] The analysis enabled us to consider that it was an acute/subacute and progressive vascular injury, with an evolving enhancing necrotic lesion due to the blood-brain barrier disruption and laminar cortical necrosis.