FAB classification of acute lymphoblastic leukemia [all] and its relevance to ALL in Karachi children

ABSTRACT

FAB classification on ALL describes three morphological variants L1, L2 and L3. Employing scoring criteria outlined by the French American and British co-workers on Romanosky stained bone marrow and peripheral blood films of eighty cases of ALL all aged below fifteen years, the following types were observed L1 55%, L2 40% and L3 nil. A small minority of cases could not fit the criteria outlined by FAB. This comprised 5% of cases with a heterogenous population of blasts with a high nuclear cytoplasmic ratio and indistinct nucleoli. These cases are either a separate variant of ALL or are undifferentiated blast cell leukaemias. We report a high frequency of L2 in our population and since L1 is associated with better prognosis within ALL, this high frequency of L2 may explain the poor prognosis observed in our children with ALL