MPO and acute myeloid leukemia: Granulocytic sarcoma, also known as chloroma because of its green color, caused by the presence of MPO, was first reported in 1823.[4] The incidence of GS is 2 per million in adults and is 2.5% to 9.1% in patients with AML.[2] Isolated GS is rare and patients usually develop to AML within several days or months.