'Lymphoid' blast crisis of chronic myeloid leukaemia is associated with distinct clinicohaematological features

It has been suggested that in blast crisis (BC) of chronic myeloid leukaemia (CML) the clinical and laboratory features of patients with 'lymphoid' phenotype differ from those of patients with non-lymphoid BC. In order to assess any differences, 97 patients consecutively diagnosed with BC that followed a known chronic phase of CML were analysed. 19 patients had 'lymphoid' BC: in 17 the blasts expressed a B-lineage phenotype; in the remaining two they corresponded to T lymphoblasts. Four cases of B-lineage phenotype BC were considered as biphenotypic, due to the co-expression of myeloperoxidase and one or two other myeloid markers (CD33, CD13 and CD68) on the blast cells; in the other six cases of B-lineage BC the blasts expressed one or both of the myeloid markers CD33 (n=4) and CD13 (n = 3), Patients with 'lymphoid' BC seldom had an accelerated phase prior to BC (1/19 v 36/78 with non-lymphoid BC, P=0.002), had less frequent splenomegaly (9/19 v 59/78, P=0.03) and hepatomegaly (5/19 v 45/78, P=0.02) and showed a higher degree of marrow blast infiltration (mean value 74+/-24% v 38+/-23%, P< 0.0001), lesser blood basophilia (2.2+/-2.5% v 8.2+/-7.8%, P<0.0001), and higher serum albumin levels (P=0.001) than those with non-lymphoid BC, 13 patients with 'lymphoid' BC (68.4%) showed a favourable response to chemotherapy regimens including vincristine and prednisone and, overall, 'lymphoid' BC patients survived significantly longer than the remainder (median survival 12 months v 4.7 months, P=0.006). These results indicate that 'lymphoid' BC of CML has a distinct clinicohaematological profile and confirm the better prognosis of such patients.