Myeloid sarcoma (MS), also termed extramedullary acute myeloid leukemia, extramedullary myeloid tumor, and granulocytic sarcoma or chloroma, is a rare manifestation that is characterized by the occurrence of 1 or more tumor myeloid masses occurring at an extramedullary site. The wide spectrum of this disorder and the conditions that it overlaps diagnostically were well reflected in the 25 cases submitted to the Society for Hematopathology/European Association for Haematopathology Workshop held in Indianapolis, IN, in November 2007. This review, on the one hand, focuses on the definition and most recent achievements on the pathobiology of MS, and on the other, also in the light of the revised World Health Organization classification, summarizes the main features of a representative series of this condition aiming to provide readers a useful document for daily practice.