Case of the Week

Background:

• T-cell lymphoma of primary central nervous system (CNS) origin is rare, representing less than 5% of all primary CNS lymphoma (PCNSL). Affected patients show diverse clinical manifestations. There is no distinct radiologic sign characteristic for T-cell PCNSL. However, it commonly presents with solitary isolated lesions in periventricular areas or multiple areas in contact with subarachnoid/subependymal surfaces.

Clinical Presentation:

• In general, patient presentation is nonspecific and can include altered mental status, focal neurologic deficits, cognitive impairment, and neuropsychiatric disturbance.

Key Diagnostic Features:

• CT: Solitary or multiple lesions in the periventricular or subependymal surfaces enhance on postcontrast imaging.
• MRI: Lesions may show areas of hyperintensity or isointensity on T2. T2 hypointensity can be present in the setting of high nuclear to cytoplasmic ratio. Moderately restricted diffusion, avid postcontrast enhancement that is usually homogeneous, and leptomeningeal enhancement may be present. Spectroscopy may show increased choline and decreased NAA.
• A distinct pattern can be seen with "lymphomatosis cerebri" that can present with multifocal patchy or diffuse hypo- or nonenhancing infiltrative-appearing lesions in the white matter.

Differential Diagnoses:

• Gliomatosis cerebri: less diffusion-restricting than lymphoma
• Inflammatory brain lesions
• Toxic and metabolic conditions

Treatment:

• Induction and consolidation chemotherapy: induction chemotherapy includes methotrexate, rituximab followed by consolidation phase of etoposide, cytarabine, and ibrutinib. Whole brain radiation is also a treatment option for those in whom chemotherapy has failed to achieve cure. Autologous stem cell transplant can also be offered to a few patients.