Primary cerebral lymphoma is seen in 6 % of AIDS patients and is the AIDS defining illness in one third of these cases. It is usually a high grade B cell non Hodgkins lymphoma, with a doubling time of only 14 days. The tumour expresses Epstein Barr virus, which can be detected in the CSF and DNA. It is commonly seen in the periventricular white matter, subependymal region, basal ganglia, thalamus and corpus callosum. 40-75 % are in contact with ependyma or leptomeninges. It is multifocal in 50 % and are usually large, > 4cm. Due to its high cellularity, the tumour is hyperdense in non contrast CT and iso to hypointense in T1 and T2W sequences. There is mass effect and edema. Contrast enhancement can be homogenous or heterogenous or ring like. Haemorrhage , calcification and necrosis are uncommon features. Leptomeningeal involvement is seen in metastatic spread from lymphoma and is usually associated with parenchymal disease.
These lymphomas in HIV paients have some differences from a non HIV patient. They occur in younger opulation, more often multiple, more prominent edema and ring enhancement.
Prognosis is bad and survival is only 3-4 months. High dose steroids and radiation are used for palliation.
Lymphoma of the posterior aspect of corpus callosum , extending into the ventricles with surrounding edema.
Another case of lymphoma.
large lymphoma in the right occipisal region , mainly in the occpial horn of the ventricle. ther eis also diffuse enhancement of the frontal horns, due to spread.
Typical dense appearance of lymphoma. In this case, the lymphoma is situated inside the ventricles.
Intraventricular lymphoma in T2W image and in sagittal images.
Focal ependymal lymphoma.
Ring enhnacing lesion in the Left parietal region. Imaging appearances are that of toxoplasmosis. But this is a proven lymphoma.
Diffuse meningeal enhancement in lymphoma