NEFL and myeloid sarcoma: Recently, based on numerous studies, NfL is considered a promising and reliable prognostic factor for patients with MS, as it well reflects the degree of disease activity, the NfL levels correlate with clinically definitive MS transformation (Kuhle et al., 2015a), they correlate with atrophy of the brain and spinal cord, the relapse rate, or worsening of disability (Kuhle et al., 2016; Petzold et al., 2016; Barro et al., 2018).