Microvessels in APL bone marrows at diagnosis and remission.

Bone marrow trephine section from an APL patient in ATRA-induced remission (A) had fewer microvessels than a diagnostic bone marrow biopsy specimen from the same patient (B). Microvessels were highlighted immunohistochemically with the use of antibodies to CD34 (brown). Original magnification, 600 ×.