Intraparenchymal, primary central nervous system lymphoma of low-grade B cell malignancy: a case report with review of the literature on therapeutic consideration

Intraparenchymal, low-grade primary central nervous system lymphomas are rare entities. We present a case of HIV negative, non-dural, low-grade primary central nervous system B cell lymphoma. A 35 year-old man presented with memory and visual disturbance. Magnetic resonance imaging demonstrated a high intensity lesion on T2 weighted images in right medial temporal lobe to basal ganglia, with irregular enhancement by gadorinium. The lesion was suspected to be high-grade glioma, however, intraoperative frozen pathology suggested lymphoma. Histopathological examination showed diffuse perivascular infiltration of small atypical lymphocyte which were positive for CD20 and CD79a. The lesion was positive for immunoglobulin heavy chain (IgH) rearrangement. Histopathological diagnosis was primary central nervous system lymphoma, low-grade B cell malignancy. The patient undertwent 5 courses of high dose methotrexate therapy (3.5 g/m²), however, recurrence was noted after therapy in brain stem. The patient was re-treated with 3 courses (4.5 g/m²), followed by whole brain irradiation. The lesion almost disappeared, and the patient is free of symptoms at 30 months from diagnosis. Although low-grade primary central nervous system lymphoma is considered relatively indolent, the present case and literature suggest that intraparenchymal, low-grade primary central nervous system lymphomas are mostly progressive, and early treatment including irradiation may be a choice.