Extramedullary infiltration at diagnosis and prognosis in children with acute myelogenous leukemia.

BACKGROUND Extramedullary infiltration (EMI) is an occasional clinical symptom in childhood acute myelogenous leukemia (AML), but there is considerable controversy regarding the prognostic significance of EMI in AML. PROCEDURE We evaluated the frequency and prognostic significance of EMI at diagnosis of AML in children. RESULTS Of 240 cases of de novo AML excluding children with Down syndrome and acute promyelocytic leukemia, 56 (23.3%) showed EMI at diagnosis. Patients with EMI had a higher initial WBC count and a higher proportion of M4/M5 morphological variants. The complete remission rate following induction chemotherapy was lower in patients with EMI. However, the overall survival and event-free survival did not differ between patients with and without EMI. A detailed analysis showed that patients with EMI with a WBC count at diagnosis of over 100 x 10(9)/L or infiltration into the central nervous system are likely to have a poor prognosis. CONCLUSIONS CNS leukemia and EMI together with a WBC count of >100 x 10(9)/L at diagnosis of AML are high risk factors for relapse, and alternative treatment approaches for patients with these characteristics should be explored.