This antibody reacts with human Carboxypeptidase A of mast cells, also known as CPA. This antibody has been used as clasification and prognosis of Systemic Mastocytosis by Flow Cytometry. Mastocytosis is a heterogeneous group of clonal mast cell (MC) disorders characterized by abnormal proliferation and accumulation of MCs in 1 or multiple tissues. Most frequently, clonally expanded MCs carry the D816V or other activating stem cell growth factor receptor gene (KIT) mutations, which translate into morphologic atypia, functional transformation, and an aberrant immunophenotype.