Analysis of paraneoplastic antibodies, including Amphiphysin, CV2, PNMA2 (Ma2/Ta), Ri, Yo, Hu, Recoverin, SOX1, Titin, Zic4, GAD65, and Tr (DNER), revealed a strongly positive anti-SOX1 antibody, assayed using the EUROLINE Paraneoplastic Neurologic Syndromes 12Ag (IgG) kit (Manufactured by EUROIMMUN [Germany]; Distributed by EUROIMMUN Japan; LOT number: D230417AN), confirming the diagnosis of paraneoplastic limbic encephalitis associated with SCLC (Supplementary Figure S1). Here, SOX1 is linked to paraneoplastic neurologic syndrome.