Evaluation of peroxidase activity by alpha-naphthol/pyronine staining compared with benzidine staining in 101 acute leukemia cases.

Cytochemical detection of myeloperoxidase (MPO) activity, a strong marker for myeloid differentiation, is usually performed by benzidine dihydrochloride staining, with the threshold at 3%. Several reports have demonstrated the potential toxicity of benzidine, and bans have been issued, under French law, prohibiting female technicians from being exposed to the aromatic hydrocarbon group, including benzidine. The aim of this study was to test an alpha-naphthol and pyronine-based substitute using a standardized kit (MYELOPEROXIDASE KIT, RAL [Réactifs RAL, Martillac, France]) to measure MPO activity in blast cells. This prospective, multicenter study made it possible to analyze 101 acute leukemia (AL) cases; it has also demonstrated both the 96% specificity and the 99% sensitivity of the method, with a threshold for positive staining of 3%, as well as good correlation (r = 0.95) between the staining method tested and the benzidine staining method. When using the alpha-naphthol/pyronine-based staining for MPO, the mean number of positive blast cells is statistically lower than that obtained using benzidine, but without incidence on AL classification. These results allow us to conclude that this method makes it possible to classify acute blood diseases by measuring MPO activity using reagents permitted by law, according to a standardized and reproducible protocol.

Clinical significance of HOX11L2 expression linked to t(5;14)(q35;q32), of HOX11 expression, and of SIL-TAL fusion in childhood T-cell malignancies: results of EORTC studies 58881 and 58951.

In a series of 153 children with T-cell malignancies enrolled in 2 consecutive European Organization for Research and Treatment of Cancer (EORTC) trials, we assessed the HOX11L2 expression and/or the presence of a t(5;14)(q35;q32). Additionally, in 138 of these patients, HOX11 expression and SIL-TAL rearrangement were also assessed. These alterations were mutually exclusive, and their frequency was 23% (n = 35), 7% (n = 10), and 12% (n = 17), respectively. HOX11L2/t(5;14) positivity was more frequent in acute lymphoblastic leukemia (ALL) with cortical T immunophenotype and in children aged between 6 and 9 years. In contrast with previously reported data, patients positive and negative for HOX11L2/t(5;14) were comparable with regard to clinical outcome as well as to the response to a 7-day prephase treatment or to residual disease at completion of induction therapy. The 3-year event-free survival (EFS) rate (+/- SE percentage) for patients positive and negative for HOX11L2/t(5;14) was 75.5% (+/- 8.1%) and 68.3% (+/- 5.0%), respectively; the hazard ratio was 0.84 (95% confidence interval, 0.40-1.80). Patients with HOX11-high expression and those with SIL-TAL fusion had low levels of residual disease at the end of induction and a favorable prognosis: the 3-year EFS rate was 83.3% (+/- 8.5%) and 75.3% (+/- 12.6%), respectively. The results obtained in HOX11L2/t(5;14) patients in this study do not confirm the unfavorable prognosis reported in previous studies.