TCRgamma gene rearrangements suggesting T clonality were seen in 11 (31%) patients, and FIP1L1-PDGFRA by RT-PCR in six (17%) of 35 patients, who showed no evidence of T-cell clonality.     ///    FISH analysis of the 4q12 deletion was concordant with FIP1L1-PDGFRA RT-PCR data.     ///    Further investigation of the nature of FIP1L1-PDGFRA affected cells will improve the classification of HES..     ///    "In the 29 patients without FIP1L1-PDGFRA, no activating mutation of PDGFRA/PDGFRB was detected. "    ///    "Sequencing FIP1L1-PDGFRA revealed scattered breakpoints in FIP1L1-exons (10-13), whereas breakpoints were restricted to exon 12 of PDGFRA. "