monoblast

The expression of CD56 suggests that the pDCs in these patients might be derived from monoblast cells.

(1991) The [Ca.sup.2+]-sensitive cytosolic phosphohpase [A.sub.2] is a 100-kDa protein in human monoblast U937 cells.

SUMMARY: The localization of peroxidase activity in different cell regions is used as a criterion for the classification of the stage of maturation of mammalian mononuclear phagocytes with a positive peroxidase reaction indicating the presence of monoblasts, promonocytes, monocytes and macrophages.

Although the morphologic test, EC stain, and FCI results clearly revealed 2 different immunophenotypes of the blast population at original diagnosis ([CD15.sup.+], [CD10.sup.-] early pre-B cell) and relapse ([CD19.sup.-] monoblast), the persistence of the t(4;11) abnormality and the presence of the immunoglobulin heavy chain gene rearrangement at relapse support the same cell of origin for both processes.

Peripheral blood smear revealed 80% monoblasts. Bone marrow aspiration revealed an 80-90% blastic infiltration with suppressed erythropoiesis and megakaryopoiesis.

Flow cytometry analysis indicates the blasts are CD34~, CD117~, CD13~, CD33+, CD14~, CD64+, CD56+, HLA-DR+, and CD123+, consistent with monoblasts. B, Bone marrow core is replaced by sheet of blasts with folded nuclei and dispersed chromatin (Wright-Giemsa, original magnification X1000 [A]; hematoxylin-eosin, original magnification X600 [B]).

Bone marrow biopsy and aspiration revealed that 65% of the bone marrow cells were monoblasts with fine chromatin, granular cytoplasm, and no Auer rods (Figure 2).

* denotes myeloblasts, thin arrows denote the monoblasts, and thick arrows denote promonocytes.