Ki67 expression in childhood acute lymphoblastic leukaemia and relation with L2 morphology

Are "early" and "late" T-acute lymphoblastic leukemias different diseases? A single center study of 34 patients

Clinical and biological parameters were retrospectively reviewed in 34 cases of T-lineage acute lymphoblastic leukemia (T-ALL), classified as "early" (20 cases) or "late" (14 cases) subgroups, according to the degree of blast cell differentiation, assessed by immunophenotyping. In "early" T-ALL, age, co-expression of "immature" (CD34 and HLA-Dr) or myeloid (My+) antigens, proliferative activity (as evaluated by Ki67 monoclonal antibody), and expression of the "multidrug-resistance" (MDR) phenotype (as determined by C-219 monoclonal antibody) were significantly higher, while WBC count and expression of CDl0 were significantly lower, than in "late" T-ALL. Furthermore, although no statistically significant difference was found between the two groups, "late" T-ALL more frequently displayed a greater extramedullary tumor mass ("lymphoma-like" syndrome), LI FAB morphology and a normal karyotype. A single patient, with "late" T-ALL, also showed positivity for TCR gamma/delta chains, specific monoclonal antibodies. On the whole, 30 patients (88.2%) achieved complete remission: 16(80%) were "early" and 14(100%) "late" T-ALL. No statistical difference was found between the two groups with respect to disease free survival (42% vs 54% at six years), whereas median overall survival was significantly shorter in "early" T-ALL (23 months vs median not yet reached at six years for "late" T-ALL, p < 0.05). We conclude that "early" and "late" T-ALL show clinical and biological differences, that could perhaps justify differential therapeutic approaches.

Monoclonal antibody Ki-67: its use in histopathology

Monoclonal antibody Ki-67 is a reliable and easy means of accurately assessing the growth fraction of human neoplasms. Although the number of long-term follow-up studies is limited, it does appear to provide valuable prognostic information particularly in lymphoproliferative disease. Since the estimation of growth fraction is only one factor influencing tumour behaviour it would be naive to believe that measurement of this parameter alone, no matter how accurately, would provide the clinician with definitive prognostic information for all tumours. The antibody is also of use in research, providing a means of measuring proliferative activity in a variety of conditions besides malignancy, and may prove of value in monitoring tumour response to established and trial therapies.