Paraneoplastic neurologic disorder (PND) is a remote manifestation triggered by altered immune response against neoplasms. Emerging discovery of antineuronal antibodies and diagnostic tool development, such as PET-CT, allow us the early recognition and treatment of these disorders.1 Neuromyelitis optica spectrum disorder (NMOSDs) is an inflammatory disease affecting the optic nerve and spinal cord, where autoantibodies against aquaporin 4 (AQP4-IgG) supposed to play a pathogenic role.2 Several tumors, such as breast cancer or carcinoid, were reported to be associated with paraneoplastic NMOSD based on immunoreactivity to de novo AQP4 in the tumor.3 One may have thought because AQP4 is expressed not only on CNS but also on muscle, kidney, and stomach,4 alteration of tumor associated self-antigens expression can cause paraneoplastic NMOSD in the tumors of these organs. However, AQP4 expression is known to decline during carcinogenesis in the gastric cancer.5 Contrary, programmed cell death ligand 1 (PD-L1) on tumor that couples with PD-1, an inhibitory receptor on both CD4+ and CD8+ T cells, to play an important role in the ability of tumor cells to escape from the host immune system.6 Indeed, 40% of patients with advanced gastric cancer express PD-L1 and proved clinical benefit by an immune check-point therapy targeting PD-1/PD-L1 axis.7 Here, we report a paraneoplastic NMOSD case with adenocarcinoma of the esophagogastric (EG) junction that exhibited immunoreactivity to AQP4 and negative for PD-L1 expression. The authors thank people in the Department of Diagnostic Pathology at Kobe University Graduate School of Medicine for their help in preparing histology sections.