Myeloid sarcomas (synonym: granulocytic sarcomas, chloromas, myeloblastomas, or monocytomas) are discrete tumors of leukemic myeloblasts or occasionally leukemic monocytes:
— These develop in skin and soft tissues, periosteum and bone, lymph nodes, gastrointestinal tract, pleura, gonads, urinary tract, central nervous system, and other sites.
— Uncommonly, they may be the first manifestation of AML, preceding the onset in marrow and blood by months or years.
— They are mistaken for large cell lymphomas by microscopy because of the similarity of the histopathology in biopsy specimens from soft tissues.
— Immunohistochemistry should be used on such lesions to identify myeloperoxidase, lysozyme, CD117, CD61, CD68/KP1, and other relevant CD markers of myeloid cells. One of four histopathologic patterns usually is evident by immunocytochemistry: myeloblastic, monoblastic, myelomonoblastic, or megakaryoblastic.
— They may usher in the accelerated phase of CML.