FLI1 and small cell lung carcinoma: Li et al. [42] found that expression of serum exosomal FLI1 exonic circRNA 1 (FECR1) was abnormally upregulated in patients with small-cell lung cancer; moreover, higher levels of exosomal FECR1 expression were observed in patients with distant metastases and serum FECR1 levels were closely related to patients’ response to chemotherapy, indicating that FECR1 could be used as a biomarker to assess the progression of small-cell lung cancer.