der(1)t(1;9): a specific chromosome abnormality in polycythemia vera? Cytogenetic and in situ hybridization studies.

Two patients with polycythemia vera and an extra der(1)t(1;9) chromosome are reported. In one patient this was found as the sole abnormality. The other patient originally presented with trisomy 9 but later developed an extra der(1) during the further course of the disease with disapperance of the extra chromosome 9.