Valuation of Cytogenetics and FISH in Evaluation of Myelodysplastic Syndromes: A Cancer Cytogenetics Reference Lab’s Experience.

Cytogenetics has proven an essential tool not only for confirming a diagnosis/classification, but for providing prognostic value as well in myelodysplastic syndromes (MDS). However, approximately 50% of primary MDS do not show discernible chromosome changes. In recent years, the fluorescence in situ hybridization (FISH) technique using gene or chromosome locus/region specific probes has emerged as a promising test in various hematopoietic and lymphoid neoplasms. To evaluate the application of FISH panels and cytogenetic studies in MDS, we retrospectively analyzed 1,885 consecutive bone marrow results from patients with suspected MDS due to cytopenia(s). In particular, we assessed the additional information a FISH reflex testing might have given in cytogenetically normal cases. The probes used in the panel included the EGR1 at 5q31, the D7S522 at 7q31, the D8Z2 for the centromere of chromosome 8, the MLL at 11q23 and the D20S108 at 20q12 (Vysis, Inc.). Among all patients, 190 (10%) had clonal chromosome abnormalities, mostly as reported in the literatures, eg, -5/5q- accounted for 34.7% of abnormalities, trisomy 8 29.5%, -7/7q- 14.2%, 20q- 13.7%. Of 345 cases with a FISH reflex test ordered and performed, only 3 (0.87%) showed positive results: a deletion of 7q31, a deletion of 20q12 and a deletion of 5q31 in 9.6%, 8.2% and 71.5% of interphase cells respectively. For the case with 5q- detected by FISH, only 12 metaphases were available for cytogenetic analysis. From our data and experience, at present, interphase FISH panel testing seems not to be an efficient and cost-effective method used as a screening test for cytopenia(s) in the diagnosis of MDS, different from its applications in B-cell chronic lymphoid leukemias, non-Hodgkin lymphomas and plasma cell neoplasms where neoplastic cells inherited not to divide easily in culture for metaphase analysis. Rather, it should be used for suspected MDS cases as a technique of choice for problematic specimens compromised for cytogenetic analysis such as cellular insufficiency, extended transit time and extremely low mitotic index or poor chromosome morphology. Until more genetic defect targeted probes become available with a better understanding of the stem cell biology and pathogenesis in MDS, cytogenetics is still the best and a “must” technique for detecting genomic aberrations in MDS and nearly all other myeloid hematopoietic neoplastic disorders.