Increased angiogenesis in bone marrow of children with acute lymphoblastic leukaemia has no prognostic significance.

The importance of angiogenesis for the growth and viability of solid tumours has been established. Similarly, prognostic information may be gained from the extent of angiogenesis in these tumours. Haematopoietic malignancies should have equal requirements for angiogenesis and important prognostic information may be derived from quantification of bone marrow angiogenic activity. We retrospectively investigated 82 bone marrow trephine biopsies from 41 children with acute lymphoblastic leukaemia (ALL) at diagnosis and following treatment. Nine normal bone marrow trephines from age-matched children were also analysed as controls. The microvessels were stained immunohistochemically with anti-Factor VIII-related antigen (antivWF) and antithrombomodulin (anti-THR). Angiogenesis was quantified manually by two independent observers and was highly reproducible (Pearson's r = 0.91). Staining with anti-vWF and anti-THR was highly specific for microvessels and thetwo stains closely correlated (r = 0.68). Microvessel densities (MVD) at presentation were significantly increased in the majority of patients in comparison with controls (P < 0.0001) and MVD dropped towards normal in remission (P < 0.0001). Of interest, the difference in total vessel counts between leukaemic and normal/remission marrows was contributed solely by small microvessels. There was no significant difference in MVD at presentation or remission from children in poor prognostic groups or those who subsequently relapsed. Similarly, we could not find an association with age, sex, cytogenetic abnormality or disease phenotype.