Primary intramedullary spinal cord lymphoma with a triple-expressor phenotype presenting as transverse myelitis and complicated by acute ischemic stroke

Background Primary intramedullary spinal cord lymphoma (PISCL) is extremely rare and often mimics inflammatory myelopathy. To our knowledge, concurrent acute ischemic stroke has not previously been described in PISCL. Case presentation A 60-year-old man developed an initial lacunar infarct (Day 0), followed by rapidly progressive bilateral lower-limb weakness (Day 7) and a thoracic intramedullary lesion with minimal cerebrospinal fluid (CSF) inflammation. A presumptive diagnosis of transverse myelitis was made, and corticosteroid and intravenous immunoglobulin therapy produced only transient improvement. On Day 9, he developed a new right middle cerebral artery (MCA) stroke requiring mechanical thrombectomy. At Week 7, follow-up spinal MRI demonstrated a new focal intramedullary lesion at T3 with homogeneous enhancement, and PET-CT showed focal hypermetabolism, leading to biopsy confirmation of diffuse large B-cell lymphoma (DLBCL) with an immunohistochemically defined triple-expressor phenotype. Treatment with rituximab, high-dose methotrexate, ibrutinib, and radiotherapy was initiated. Outcome Despite therapy, neurological function worsened, and the patient progressed to paraplegia. Conclusion This case highlights the diagnostic challenges of PISCL presenting as inflammatory myelopathy and supports consideration of earlier tissue diagnosis when the clinical course is progressive and steroid responsiveness is only transient. The accompanying ischemic stroke may have reflected multiple contributing factors, but causality cannot be established from a single case. The immunohistochemically defined triple-expressor phenotype should be interpreted cautiously in the absence of cytogenetic confirmation of MYC/BCL2/BCL6 rearrangements.