Extramedullary involvement in acute lymphoblastic leukemia and its relation to therapy.

Extramedullary involvement (EMI) of various body sites was studied by doing CSF cytology anu FNAC of testes and lymph nodes in 82 children with acute lymphoblastic leukemia (ALL). Forty-five patients had received no therapy (group I) and 37 had been diagnosed and treated earlier and were now in remission (36) or relapse (group II). EMI was documented in 48.9% and 32.4% of patients of group I and II respectively. EMI was seen more frequently in patients with FAB-L 2 subtype (66.6%) as compared to FAB-L 1 subtype (34.6%) in group I. Lymph nodes and testes were commonly involved in group I and II patients respectively. Successful remission after complete chemotherapy was achieved in 82.5% of group I patients. However, successful remission rates were 95.2% in patients without any evidence of EMI versus 68.4% in those with EMI. These differences were also observed when response to therapy was analysed separately for patients with FAB-L1 and FAB-L2 subtypes.