[Acute leukaemia with lymphoblastic features occurring during myeloma (author's transl)].

: Leukaemias which complicate myeloma under treatment are usually acute non-lymphocytic leukaemias. We report here a case of acute leukaemia with lymphoblastic features occurring 30 months after diagnosis of myeloma. The exceptional character of this association lead us to refine the cytological diagnosis by studying surface markers and ultrastructural cytochemistry. Because of the absence of T or B markers, and the absence of peroxidase activity in the nuclear envelope, the endoplasmic reticulum, and the Golgi apparatus of blastic cells, we conclude that this leukaemia is "null" lymphoblastic.