These categories should be applied to patients with MMM (both idiopathic and post-polycythemia vera [post-PV] or post-essential thrombocythemia [post-ET] myelofibrosis) receiving both palliative and disease-modifying therapies. The 3 categories of response should be used in a cumulative sequential manner starting from the clinicohematologic response (thus representing the minimal set of criteria to be evaluated for assessing response). The decision to use a composite definition of response (clinicohematologic and histologic response; or clinicohematologic, histologic, and cytogenetic response) will depend on the goal of the therapy.