CD34 and acute lymphoblastic leukemia: In the BM aspirate, blasts with a high N/C ratio with prominent cytoplasmic vacuolation and blebbing accounted for 53% of nucleated cells morphologically (Figure 1(c)) and were CD34+, CD19+, HLA DR+, CD20+, CD38+, TdT+, and CD10− by multicolor flow cytometry and CD34+, PAX5+, TdT+, CD10−, and MPO− by immunohistochemistry, consistent with a diagnosis of pro-B ALL.