NEFL and cancer: 2019). When malignant tumors metastasize, alterations in the tumor microenvironment and damage to host tissues result in increased NfL levels (Kim et al. 2024). Additionally, paraneoplastic syndromes triggered by certain malignant tumors and chemotherapy drugs can cause neuropathy, further increasing NfL levels (Constantinescu et al. 2017; Wang et al. 2025).