Secondary Central Nervous System Lymphoma Involving Meninges: A Rare Case Report and a Comprehensive Review of Peripheral T-Cell Lymphoma, Not Otherwise Specified.

Peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS), is a rare and aggressive subtype of non-Hodgkin lymphoma (NHL) that arises from mature T or natural killer (NK) cells, accounting for about 5% of all NHL cases. While PTCL-NOS typically involves lymph nodes, extranodal sites such as the skin, gastrointestinal tract, liver, and lungs can also be affected. Central nervous system (CNS) involvement is extremely rare, especially at the time of initial presentation. When it does occur, the brain is most commonly affected, followed by the spinal cord and meninges. We present a rare case of PTCL-NOS with secondary CNS lymphoma involving the meninges at initial diagnosis. Our patient is a 75-year-old male with multiple comorbidities who presented with several weeks of intermittent headaches. Imaging showed multiple extra-axial brain lesions with infiltration into extracranial soft tissues, epidural space, meninges, and brain parenchyma. A subsequent lymph node biopsy confirmed PTCL-NOS. He was started on rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP), with plans for high-dose methotrexate. Thereafter, the patient was readmitted several times due to various complications and expired approximately 2.5 months after diagnosis. We conclude that secondary CNS involvement in PTCL-NOS is very rare and has a poor prognosis, with a median survival after CNS diagnosis of about 1.1 months. Early diagnosis and tailored treatment strategies, including CNS-penetrating agents, are essential. Continued research is needed to better understand and improve outcomes for this aggressive disease.