This MRI scan shows a large multilobulated mass centered in the right frontal lobe. It homogeneously enhances with contrast and shows significant mass effect with distortion of the lateral ventricles. The biopsy was diagnostic of a diffuse large B-cell lymphoma. Case courtesy of A.Prof Frank Gaillard, Radiopaedia.org. From the case rID: 5530 Primary CNS lymphomas tend to be parenchymal based and are usually supratentorial. The frequent sites of involvement are the frontal (most common), temporal, or parietal lobes and basal ganglia. Involvement of cerebellum and spinal cord is rare. Leptomeninges may be secondarily involved (30% to 40% of cases). The lesions may be solitary or multiple (25% to 50% of cases) and poorly circumscribed with displacement of normal structures. Multifocal lesions are more likely to be seen in immunocompromised patients (although this patient was immunocompetent).