Selected cytogenetic and FISH results for patients 2 and 3. (A) Patient 2 partial karyotype showing t(4;12) (top panel). 4q12 metaphase FISH analysis shows 1 normal chromosome 4 [chr(4)] with overlap of all 3 probes, the SpectrumAqua (PDGFRA) probe on the derivative chromosome 12 [der(12)], and the SpectrumGreen (SCFD2) probe on the derivative chromosome 4 [der(4)] (middle panel). There is loss of 1 SpectrumOrange signal, indicating loss of LNX1 or adjacent material. ETV6 break-apart metaphase FISH analysis shows 1 normal chromosome 12 [chr(12)] with overlap of the 5′ ETV6 SpectrumOrange and 3′ ETV6 SpectrumGreen probes, the derivative chromosome 12 [der(12)t(4;12)] with 3′ ETV6 SpectrumGreen and dim 5′ ETV6 SpectrumOrange signals, and the derivative chromosome 4 [der(4)t(4;12)] with the 5′ ETV6 SpectrumOrange probe only (bottom panel). (B) Patient 3 partial karyotype showing t(4;12) (top panel). 4q12 interphase FISH showing 1 normal tricolor signal, 1 separate SpectrumGreen (SCFD2)/SpectrumOrange (LNX1) overlap signal, and 1 isolated SpectrumAqua (PDGFRA) signal (middle panel). ETV6 interphase break-apart FISH showing 1 isolated ETV6 5′ signal in addition to 1 normal unsplit pair and 1 unsplit pair with dim 5′ ETV6 signal (bottom panel).