Current and possible future classification process of MDS. (A) MDS hierarchical classification process according to current ICC and WHO5. Morphologic features affecting classification are on the left and genetic determinants are on the right. Subtypes that are common to both ICC and WHO5 are shown in green, ICC subtypes are in yellow, and WHO5 subtypes are in orange. The detailed diagnostic criteria and exclusionary features of each entity are not shown on this diagram and are provided in separate publications.^5,6 (B) A possible future classification approach that would separate the current hierarchical interweaving of morphologic and genetic MDS subtypes. Genetic classes are shown on the left and would be based on molecular clustering analyses of MDS cohorts; each case would be assigned a genetic class at diagnosis. Independent of the genetic class, the diagnosis of each case would include morphologic information, shown on the left. These morphologic data would reflect disease stage and treatment response (blasts) and express phenotypic features that provide additional prognostic information (SLD vs MLD, fibrosis grade) or guide therapy (hypocellularity), depending on the specific genetic class and patient characteristics. Professional illustration by Somersault18:24.