Cytogenetics

Conventional cytogenetic evaluation of patients with MF often fails presumably because of marrow fibrosis precluding obtaining sufficient cells on aspiration. Fibrosis was shown to be a secondary process as fibrob-lasts in culture were either cytogenetically normal or had clones that differed from the marrow.43 A normal karyotype is at least as frequent as an abnormal one; furthermore some studies suggest an associated prognostic significance.44 In a larger study reported by Tefferi45 90% of abnormalities were either +8, +9, del(20)(q11q13), del (13)(q12q14), and del(12)(p12) or involved chromosomes 1 or 7. Here only +8 or del(12)(p12) appeared to be independent prognostic indicators.

Of interest is the fact that chromosome 13 abnormalities (del(13)(q12q14) or translocations involving this region) appear to be consistently present both in primary MF and, most likely, as a second event in MF which evolves in the other MPDs.46'47 The del(13) (q12q14) potentially results in the loss of RB, a well-characterized tumor suppressor gene, and this has indeed been demonstrated but only in a proportion of patients with MF.48

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