Neurolymphomatosis of multifocal peripheral nerve involvement: a case report.

The infiltration and invasion of nerve trunks, nerve roots, and cranial nerves by lymphomatous malignant cells is defined as "neurolymphomatosis". It is mainly caused by lymphoma cells directly infiltrating the peripheral nerves, with a low incidence. Neurolymphomatosis is a rare condition of neoplastic endoneurial invasion, which is primary or secondary to non-Hodgkin's lymphoma and leukemia. We describe a case of primary peripheral neurolymphomatosis of multifocal involvement in a 77-year-old male patient. He presented with left lower limb pain and was diagnosed with CD20+ diffuse large B cell lymphoma (DLBCL). Magnetic resonance imaging (MRI), fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) computed tomography (CT), and nerve biopsy contributed to the diagnosis. Genomic profiling, programmed death ligand-1 (PD-L1) expression and tumor mutational burden (TMB) were also assessed. CDKN2A/CDKN2B deletions have been identified. PD-L1 expression assessed by 28-8 antibody was 1% positivity, and TMB of the sample was 11.6 muts/Mb. The patient responded well to rituximab combined with chemotherapy, however, he died after 3 cycles of chemotherapy due to severe lung infection and subsequent complication of respiratory failure. Here we report the clinical, radiological, pathological and molecular findings of the patient affected by multifocal neurolymphomatosis without systemic involvement of other organs.