ABSTRACT
BACKGROUND: In acute lymphoblastic leukemia (ALL), the importance of argyrophilic nucleolar organizer regions (AgNOR) is not established. METHODS: NOR silver staining was carried out in 74 ALL patients. We analyzed the AgNOR parameters ; counting parameters including number of AgNOR per cell, percentage of cells with one cluster, and area parameters including mean AgNOR area, total AgNOR area, and its percentage of nuclear area by morphometry. Cyclin A index was evaluated by immunohistochemical stain. We compared the AgNOR parameters with cyclin A index and evaluated the differences of AgNOR parameters in accordance with FAB classification, immunophenotype, a new classification of ALL (ALL with maturation), and response to induction chemotherapy. RESULTS: A positive correlation was found between cyclin A index and AgNOR area parameters and a significant negative correlation was found between mean AgNOR area and number of AgNOR per cell (r=-0.433, P=0.000). AgNOR area parameters revealed the highest value in L3. The number of AgNOR per cell in T cell ALL was higher than non-T cell ALL (P=0.011), and the percentage of cells with one cluster was lower (P=0.002). The number of AgNOR per cell in ALLm was lower (P=0.004) and the percentage of cells with one cluster was higher than in typical ALL (P=0.002). In cases achieved complete remission (CR) after induction chemotherapy, the number of AgNOR per cell was higher (P=0.005) and the percentage of cells with one cluster was much lower than in cases failed to achieve CR (P=0.013). CONCLUSIONS: Our study indicates that the AgNOR area parameters are helpful to predict the proliferating activity of leukemic blasts in ALL. It is suggested that the number of AgNOR per cell and the percentage of cells with one cluster provide a valuable information to estimate the response to chemotherapy in ALL.