What additional feature is considered in the WHO classification of myelo- and lymphoproliferative disorders?

The inclusion of cytogenetic abnormalities in the WHO classification of myelo- and lymphoproliferative disorders is crucial because these abnormalities provide significant insight into the genetic alterations that drive these diseases. Cytogenetics involves the study of chromosomes and can reveal often-targeted changes such as translocations, deletions, and amplifications that are characteristic of specific hematological malignancies.

By identifying these cytogenetic features, clinicians can better classify the disorders, understand prognosis, and tailor treatment strategies. For instance, certain cytogenetic abnormalities are associated with more aggressive diseases or poorer outcomes, while others may indicate a more indolent course or response to specific therapies.

The other options, while interesting in their own contexts, do not have the same established prominence in the WHO classification system compared to cytogenetic abnormalities. Proteomics, for instance, refers to the study of proteins and their functions, which can also be important but is not a primary classification criterion. Similarly, carbohydrate-associated tumor antigens and cell signaling and adhesion markers provide valuable information about disease mechanisms but do not typically play a direct role in the classification according to the WHO. Thus, the emphasis on cytogenetic abnormalities reflects their critical role in defining the nature and behavior of myelo- and