DIFFERENTIAL-DIAGNOSIS BASED ON IMMUNOLOGICAL PHENOTYPING IN SUSPECTED MALIGNANT BONE-MARROW INVOLVEMENT IN CHILDHOOD

The diagnostic value of immunophenotyping (IP) as a first-line diagnos tic method in diseases that infiltrate the childhood bone marrow (BM) or mimic infiltrated BM was examined. Two hundred and fifty unselected BM samples from 250 children suspected to have a malignancy infiltrat ing their BM were evaluated by means of IP and conventional morphologi cal-cytochemical (MC) studies. We applied the alkaline phosphatase ant i-alkaline phosphatase method for IP using a panel of monoclonal antib odies (Mabs) against leukocyte-associated antigens, neuroectodermal an tigens, and intermediate filament antigens. Four cases of neuroblastom a, two cases of Ewing sarcoma, and one case of rhabdomyosarcoma were d iagnosed by IP but not by MC studies. In nine cases of acute leukemia bone marrow blasts could not be ascribed to a specific lineage on the basis of blast morphology or histochemistry. Eight samples without mor phological evidence of malignant infiltration revealed an Increased pe rcentage of immature B cell precursors (CD10(+), TdT(+)) suggesting ac ute lymphoblastic leukemia. None of these children has developed malig nant lymphoproliferative disease. Our data suggest that the immunologi cal evaluation of BM In childhood is highly capable of discriminating between different malignant populations but it does not recognize mali gnancy and therefore supplements but cannot replace conventional metho ds for diagnosis.