PF4 and cutaneous mastocytosis: While no clear biomarker with sufficient diagnostic power to be used in the clinic exists for CM to date, some prognostic biomarkers associated with a fatal outcome in pediatric CM have been identified, such as low levels of Angiopoietin-1 (17) and high levels of Angiopoietin-2 (18), CXCL10, and CXCL4 (19).