A Rare Case of Primary Central Nervous System Lymphoma in an Adolescent Female Treated with High-Dose Methotrexate and Rituximab-Based Chemoimmunotherapy and Consolidation Whole Brain Radiotherapy.

Primary central nervous system lymphoma (PCNSL) is a rare pediatric brain tumor. A 16-year-old female patient presented to the clinic with complaints of multiple episodes of generalized tonic clonic seizures, nystagmus, and weakness on the left side of the body for 3 weeks. She had similar symptoms, waxing and waning for the last 2 years, responding to corticosteroids. Repeat magnetic resonance imaging (MRI) of the brain showed multiple areas of signal abnormalities involving the left temporal lobe, the basal ganglion, the thalamus, and the right frontal and occipital lobes with contrast enhancement in bitemporal lesions. With a clinico- radiological diagnosis of demyelinating disorder, she underwent an image-guided right frontal lobe biopsy, which revealed sheets of atypical lymphoid cells diffusely immunopositive for CD20 but negative for CD3, CD10, BCL-6, and MUM-1, suggesting diffuse large B-cell lymphoma, germinal center B-cell subtype. The systemic lymphoma workup was essentially normal. She received 5 cycles of chemoimmunotherapy with rituximab, high-dose methotrexate (HDMTX), vincristine, and procarbazine and had a complete radiological response (CR). This was followed by whole brain radiotherapy (WBRT) to a dose of 36 Gy in 20 fractions over 4 weeks. Subsequently she received 2 cycles of consolidation chemoimmunotherapy with rituximab and high-dose cytarabine. Serial brain MRI done 1, 4, and 8 months after completion of treatment showed persistence of the CR. At the last follow-up visit, 15 months from the date of diagnosis, she was disease free and asymptomatic. This report underlines the fact that PCNSL in adolescents may be effectively treated with a combination of HDMTX- and rituximab-based chemoimmunotherapy followed by consolidation with WBRT.