Harmonization of Diagnostic Criteria in Mastocytosis for Use in Clinical Practice: WHO Vs ICC Vs AIM/ECNM

Mastocytosis is a clonal myeloid disorder defined by an increase and accumulation of mast cells (MC) in one or multiple organ systems. The complex pathology of mastocytosis results in variable clinical presentations, courses, and outcomes. The World Health Organization (WHO) divides the disease into cutaneous mastocytosis (CM), several forms of systemic mastocytosis (SM), and MC sarcoma. In most SM patients, a somatic KIT mutation, usually D816V, is identified. Patients diagnosed with CM or non-advanced SM, including indolent SM, have a near-normal life-expectancy, whereas those with advanced SM, including aggressive SM and MC leukemia, have limited life-expectancy. Since 2001, a multidisciplinary consensus group consisting of experts from the European Competence Network on Mastocytosis (ECNM) and American Initiative in Mast Cell Diseases (AIM), has supported the field by developing diagnostic criteria for mastocytosis. These criteria served as the basis for the WHO classification of mastocytosis over two decades. More recently, an international consensus group (ICC) proposed slightly modified diagnostic criteria and a slightly revised classification. In this article, these changes are discussed. Furthermore, we propose harmonization among the proposals of the AIM/ECNM consensus group, WHO, and ICC. Such harmonization will facilitate comparisons of retrospective study results and the conduct of prospective trials.