Figure 2 : Fluorescence in situ hybridisation shows t(7;12) rearrangement.

The ideograms on the left show possible patterns of hybridisation using the dual colour break-apart probe (A and G). A straight forward t(7;12)(q36;p13) translocation results in the juxtaposition of green and red signals on the der(7) and the der(12), whereas the normal chromosome 7 carries only red signals and the normal chromosome 12 carries only green signals (A). This is visible on the metaphase chromosomes (B). In the nuclei it is possible to visualise one green signal and one red signal as well as two red-green signals (C-E). By the analysis of interphase FISH alone, it is not possible to discriminate between the two derivatives, although it is assumed that one would be a der(7) and the other one would be a der(12) (F) Images B-E were obtained using patient no. 3 sample. A different hybridisation pattern is shown on the sample from patient no. 4, where the der(7) involved in the translocation is also affected by a deletion. This results in a shorter chromosome 7 carrying only green signals and a der(12) carrying green-red signals, whereas the normal chromosomes 7 and 12 carry red only and green only signals respectively (G and H). In the interphase nuclei it is possible to identify confidently the der(12) as a green-red signal in this case, whereas the normal chromosome 7 is identified by red signals alone. Green signals may indicate the normal chromosome 12 or the der(7), although it is noted that in most nuclei one of the two green signals is smaller, indicating the der(7) (I-J).

Tosi et al.Hematology and Leukemia  2015 3:4DOI : 10.7243/2052-434X-3-4