B-cell acute lymphoid leukemia (ALL) with lymphoblasts expressing surface immunoglobulins only at relapse.

Morphological, cytogenetic and immunological studies were performed on lymphoblasts of two patients with acute lymphoid leukemia at onset and at relapse. At onset and before any treatment lymphoblasts had L3-FAB morphology, a 14q+ chromosome abnormality due to a 8;14 translocation in the absence of expression of specific immunologic markers (E-rosette, C3-receptor, surface immunoglobulins). The clinical behaviour of the two patients was characterized by a very short first complete remission and by a short survival. At relapse SIg was expressed by lymphoblasts of both patients. This evolution in immunological phenotype of the dominant blast populations from onset to relapse provides evidence that in vivo, during the course of the leukemic disease, phenotype changes take place that seem to be cell differentiation.