Acquired Trisomy 12 and Absent Y Chromosome in a Patient with Acute Undifferentiated Leukaemia

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Abstract
A 60 yr old man developed pancytopenia and then acute leukemia. The neoplastic cells in marrow were undifferentiated by EM and by immunological and cytochemical markers. The only other cells present in marrow were lymphocytes, plasma cells, macrophages and non-hematopoietic elements. Prior to chemotherapy, cytogenetic analysis of marrow cells showed 2 karyotypically distinct cell populations, one with 45,X,-Y and the other with a 46,X,-Y, +12 karyotype. All marrow cells stimulated by protein-A from Staphylococcus aureus were 46,X,-Y, +12. Phytohemagglutinin-stimulated cells were normal, 46,XY. Most of the undifferentiated leukemic cells were missing the Y chromosome. A subpopulation of these leukemic cells also had trisomy 12. Trisomy 12 apparently occurs non-randomly in hematological disorders and may be associated with B-lymphoid malignancy in particular.