<prompt> Primary cerebral lymphoma -It is most common formed of T cellsIt is usually solitaryMultifocal-lesion are seenIt is seen in immunosuppressed patient  <response>: Primary CNS lymphoma are high grade B cell lymphomas associated with EBV infection .Characteristically ,imaging shows a single,homogenously enhancing ,periventricular lesion with surrounding oedema.Brain biopsy is definitive.Prognosis is very poor. Reference: Harrison20th edition pg 897 