Immunological subtypes of childhood acute lymphoblastic leukemia in Bulgaria

With regards to the geographical variation in acute lymphoblastic leukemia (ALL) distribution, we present data from the immunophenotyping of 171 newly diagnosed cases of childhood ALL in Bulgaria during a 4 year period (1990-1994). On the basis of 17 phenotypic markers the distribution of immunological subtypes was as follows: AUL 4%; Pro-B ALL 13%; common ALL 42%; Pre-B ALL 11%; B-ALL 1%; T-ALL 28% and unclassified 2%. Most of the cases were between 2 and 5 years of age. Common ALL was predominant (53%) in this age group. The male:female ratio was 1.7:1. The frequency of T-ALL (28%) was significantly higher (P < 0.01; t = 3.49) in comparison to that reported for the U.S.A. and West European countries (mean 13%). It was close to the frequency reported by some authors for France (20%), Greece (26%) and south Italy (28.1%). These countries and Bulgaria might form an environmental area with a moderate frequency of T-ALL.