POSTN and cancer: Periostin has already proven its usefulness as a biomarker in fibrotic diseases and in cancer states [25,45], owing this to some of its features: it is increased in many pathological states in the urine, blood, and sputum, thus proving that is readily secreted from injury sites, the concentration of serum periostin revolves around the ng/mL domain (≈10 ng/mL), an appropriate magnitude for a precise detection of variations in the investigated site [13,46].