Microvessel density and hot spot density in APL bone marrows at diagnosis and remission.

Microvessel density in bone marrow biopsy specimens obtained from patients (n = 7) in ATRA-induced remission (■, 4.2/hpf) was significantly decreased (P = .0063) compared with microvessel density (8.1/hpf) in diagnostic bone marrow biopsy samples from the same patients (▪). Hot spot density in bone marrow biopsy specimens from APL patients in ATRA-induced remission (10.4/hot spot) was also significantly (P = .0159) lower than hot spot density (17.3/hot spot) in their corresponding diagnostic bone marrow biopsy specimens.