Breast tumour as a first manifestation of extramedullary relapse in acute lymphoblastic leukaemia.

After 2 years of maintained complete remission, a 17-year old girl suffering from common acute lymphoblastic leukaemia (C-ALL) developed a mass in the right breast. Determination of the tumour cell phenotype using a panel of monoclonal antibodies demonstrated the presence of leukaemic blasts. At this stage no other sign of relapse could be demonstrated. Later, however, when the leukaemia progressed despite aggressive treatment, blasts with the same surface phenotype as the ones in the breast were obtained both from repeated biopsies from a mediastinal mass and from a lower abdominal mass. Manifestation of first relapse in ALL presenting as a breast tumour has never been described before and may be added to other unusual extramedullary sites of relapse. The significance of immunologically defined phenotyping of cells from tissue biopsies is underlined.