Acquired form of immunodeficiency-associated CNS lymphoma is a subset of primary CNS lymphoma which is mostly due to HIV/AIDS, as in this case. It occurs when the CD4 count is less than 50cells/ul. They have a good initial response for steroid treatment, though generally have poor prognosis. The response to steroids can be used to retrospectively confirm the radiological diagnosis.

Radiological differential diagnosis in this case was butterfly glioma/glioblastoma. The large necrotic component of the mass was suggestive of glioma than lymphoma, though lymphoma in immunocompromised can also have necrotic component. Biopsy was done in this patient after two weeks of steroid treatment and the histopathology result was negative. It is advised to withhold steroids , if possible, before biopsy of lymphoma as steroid reduces the diagnostic yield by up to 50%.