FSTL1 and breast cancer: The dominant component of breast tissue stroma, adipose tissue, is composed of adipocytes, which secrete various cytokines, including adipokines, whose role in breast cancer is not fully understood.<h4>Methods</h4>In this study, selected new adipokines were measured for the first time, including: progranulin (PGRN), follistatin-like protein 1 (FSTL1), asprosin (Asp), meteorin (METRN), adipsin (CFD), nesfatin (NES1), neuregulin 4 (NRG4), and isthmin (ISM1) in the serum of breast cancer patients, divided according to the molecular subtype and grade of the tumor.