Ultrastructural study of B-bodies in leukapheresed cells of patients with acute leukemia.

Peculiar inclusions, which we call B-bodies, have been observed in cells collected by leukapheresis from patients with acute leukemia. B-bodies, which often have virus-like features, were present in blast cells of 24 (44%)( of the 54 patients examined; in 16 out of 29 with acute myelogenous leukemia, 5 out of 16 with acute lymphoblastic leukemia, 2 out of 3 with undifferentiated leukemia, and 1 out of 2 with myelogenous leukemia in blastic transformation. The ultrastructure of these apparently polymorphic inclusions was always based on a system of of cytoplasmic channels containing dense, axial filaments. Patients with B-bodies were mostly women near menopause (70% of the positives).