Myeloid Sarcoma: Kidney
Section Editor: Dharam M. Ramnani, MD
Virginia Urology, Richmond, VA, USA
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Myeloid sarcoma is a solid tumor consisting of extramedullary proliferation of myeloid precursors, including myeloblasts, promyelocytes, and myelocytes. It has also been referred to as chloroma, granulocytic sarcoma, or extramedullary myeloid tumor. It may or may not be associated with a myeloid neoplasm in the bone marrow. Myeloid sarcoma is considered diagnostic of acute myeloid leukemia (AML) and should be classified and treated accordingly, regardless of the bone marrow or peripheral blood status. It may be the first manifestation of an acute leukemia or may signal relapse in a previously treated patient. It may also signal transformation to acute leukemia in patients with myeloproliferative disorders or myelodysplastic syndromes.
Gross Pathology: Myeloid sarcomas are fleshy tumors that may exhibit characteristic greenish hue (the basis for the term chloroma; chloros = pale green in greek). The green color is notable in tumors with granulocytic differentiation and is due to high levels of the enzyme myeloperoxidase (previously known as verdoperoxide) in the cytoplasmic granules of neoplastic cells. The green color fades in 2 to 3 hours upon exposure to air due to oxidation of the enzyme. About 60-70% of tumors are not green, hence the term chloroma is no longer preferred. The appearance of the tumor may be white, gray, or brown depending upon the concentration levels of myeloperoxidase and its oxidation status in the blasts.
This autopsy specimen from a patient with acute myeloid leukemia shows rather striking green tumor (myeloid sarcoma) involving the kidney.
Gross Pathology: Myeloid sarcomas are fleshy tumors that may exhibit characteristic greenish hue (the basis for the term chloroma; chloros = pale green in greek). The green color is notable in tumors with granulocytic differentiation and is due to high levels of the enzyme myeloperoxidase (previously known as verdoperoxide) in the cytoplasmic granules of neoplastic cells. The green color fades in 2 to 3 hours upon exposure to air due to oxidation of the enzyme. About 60-70% of tumors are not green, hence the term chloroma is no longer preferred. The appearance of the tumor may be white, gray, or brown depending upon the concentration levels of myeloperoxidase and its oxidation status in the blasts.
This autopsy specimen from a patient with acute myeloid leukemia shows rather striking green tumor (myeloid sarcoma) involving the kidney.