Masked monosomy 7 in myelodysplastic syndromes is uncommon and of undetermined clinical significance

Masked monosomy 7, i.e. detected by FISH but not by conventional cytogeneti cs, has been reported in varying frequency in MDS. To establish the prevale nce and possible clinical significance of the aberration, we studied the 12 3 previously karyotyped MDS patients using FISH and a DNA probe specific fo r chromosome 7. Metaphase cytogenetics revealed ten patients (8%) with mono somy 7 (6 RAEB and 4 RAEB-t). FISH confirmed this result and detected four more cases (4%) with masked monosomy 7 (3 RA and 1 RARS). Thus, masked mono somy 7 is less common than has been suggested, and does not seem to carry t he same prognostic weight as monosomy 7 diagnosed by metaphase cytogenetics . (C) 2001 Elsevier Science Ltd. All rights reserved.