Karyotypic identification of abnormal clones preceding morphological changes or occurring with no definite morphological features of myelodysplastic syndrome: a preliminary study.

The diagnosis of myelodysplastic syndrome (MDS) is difficult to establish based on morphologic features alone because dysplasia may not always be detectable and the presence of dysplasia is not itself evidence of clonal disorder. As a result, the detection of a clonal cytogenetic abnormality has a major role in difficult cases in regard to diagnosis and the recognition of morphological cytogenetic correlates. In an attempt to assess the frequency and characteristic type of abnormal clones when it is not clear whether or not a hematological condition is neoplastic, cytogenetics have been analyzed necessarily in 159 patients with unexplained cytopenia or suspected MDS. We found 14 patients (8.8%) with cytogenetic abnormalities in the absence of concomitant dysplastic features of the marrow at diagnosis. The cytogenetic changes were characteristic of those reported for myeloid malignancies: 3 del(20q), 2 Y chromosome losses, 2 del(5q), 2 11q23 abnormalities, and one each of t(3;5), i(7q), trisomy 8, and del(13q). One case of ring chromosome 4 was also found. A few months later, 3 of these patients showed marrow changes consistent with MDS. Our data demonstrated that a significant proportion of otherwise uncertain diagnoses presented abnormal clones. Long-term follow-up will be required to help determine the malignant potential of these clones.