Myeloid sarcoma is a tumor mass made up of immature myeloid cells.
Features of myeloid sarcoma:
(1) tumor mass of myeloblasts and/or immature myeloid cells and/or monoblasts
(2) can occur in an extramedullary site anywhere in the body or in bone
(3) can occur with acute myeloid leukemia, chronic myelogenous leukemia, other myeloproliferative neoplasm, or myelodysplastic syndrome in transformation
The appearance of a myeloid sarcoma may precede the diagnosis of acute myeloid leukemia by months or years.
Tumors cells stain with immunohistochemical stains against myeloid antigens: CD7, CD13, CD33, CD117, MPO, CD43.
Monoblastic sarcoma is a tumor mass composed predominantly of monoblasts. This shows staining with monocytic antigens (CD14, CD116, CD11c, CD68, lysozyme).
