Mastocytosis is a heterogeneous group of neoplasms that involve the clonal expansion of mast cells into one or more organ systems, which typically involves the skin and hematopoietic systems. Systemic mastocytosis consists of a multifocal infiltration of mast cells into various noncutaneous tissue sites, especially the bone marrow. Diagnosis requires tissue confirmation, and algorithms have been developed to assist clinicians in this process. The current classification system focuses on delineating prognostic categories. Therapeutic approaches include symptomatic management, prevention of complications, and, in advanced disease, cytoreductive therapy.