12P-CHROMOSOMAL ABERRATIONS IN PRECURSOR-B CHILDHOOD ACUTE LYMPHOBLASTIC-LEUKEMIA PREDICT AN INCREASED RISK OF RELAPSE IN THE CENTRAL-NERVOUS-SYSTEM AND ARE ASSOCIATED WITH TYPICAL BLAST CELL MORPHOLOGY

Recently we reported cytogenetic, clinical, and immunologic data of 13 5 childhood ALL patients, who were diagnosed and treated in The Sophia Children's Hospital between January 1, 1980 and November 1, 1990. An increased risk for a first relapse in the central nervous system (CNS) was detected in a subgroup of childhood ALL patients with common ALL or pre-B ALL phenotype and chromosomal aberrations of the short arm of chromosome 12. In this paper we report clinical, cytogenetic, immunol ogic, morphologic and cytochemical data on these eight childhood ALL p atients with aberrations of the short arm of chromosome 12 and of an a dditional four cases that were diagnosed and treated between November 1, 1990 and February 1, 1992. We found that three out of six common AL L, two out of three pre-B ALL and one out of three T-ALL patients with 12p chromosomal rearrangements developed a first relapse in the CNS. On the contrary, the frequency of CNS relapse in our childhood ALL pat ients without 12p aberrations was 10%. Furthermore, morphologic and cy tochemical analysis of the bone marrow smears of these 12 patients wit h aberrations of the short arm of chromosome 12 revealed that the nine cases with pre-B or common ALL phenotype had typical morphologic char acteristics that are unusual for newly diagnosed childhood ALL. Typica l for this subtype is the presence of large polymorphic blast cells wi thout nucleoli. The nuclei are irregularly shaped showing folds and cl efts and a stripy pattern. The nucleus and cytoplasm are often abundan tly vacuolated. The cytoplasm has a foamy light-blue appearance.