CHANGES IN CYTOMORPHOLOGY OF CHILDHOOD LYMPHOBLASTIC-LEUKEMIA AT THE TIME OF DISEASE RELAPSE

Aims-Children in a United Kingdom national trial for relapsed non-B ly mphoblastic leukaemia (ALL) had their diagnostic and relapse marrow cy tomorphology compared to see what changes occur during the evolution o f the disease. Methods-Each relapse slide was assessed blindly for Fre nch American British (FAB) type and other morphological features by a panel of three independent microscopists without reference to each oth er or any diagnostic material. Diagnostic slides had been assessed by the same panel on an earlier occasion. Results-A total of 134 consecut ive children was studied. Six (5%) were classified as FAB type L2 at d iagnosis, compared with 18 (13%) at relapse (a difference of 9%). Twen ty two (16%) changed their FAB type, 17 (13%) from L1 to L2 and five ( 4%) from L2 to L1. The FAB score fell at relapse in 34 children and ro se in 14, a difference of 14%. Cell size was the commonest feature to change (increasing in 22 and diminishing in nine) followed by prominen t nucleoli (appearing in 21 and disappearing in six). Forty four (33%) children had vacuolated blasts at diagnosis, compared with 48 (36%) a t relapse. Twenty five changed their vacuole score substantially, 14 g aining > 10% and 11 falling < 10%. Conclusions-These findings reflect the variability of lymphoblast cytomorphology, but also show a trend f or cells to have more prominent nucleoli and greater size at relapse. Factors controlling these features of the FAB type are unknown, but th ey may simply be related to the growth fraction of a particular diseas e and not to any lineage specific biological feature.