PMC4408675_01
Renal Ewing sarcoma with EWSR1/FLI1 fusion. (a) Lobar architecture with Homer-Wright rosettes (H and E). (b) Immunohistochemistry with anti-CD99 (Leica, NCL-CD99). (c) Immunohistochemistry with anti-NKX2.2 (Sigma, A71669). (d) Touch imprint smear. Tumor cells have round to oval nuclei with coarsely granular chromatin (Pap). (e) The tumor cells show cytoplasmic expression of CD99. (f) The tumor cells show strong and diffuse nuclear expression of NKX2.2
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F1
A needle biopsy of the renal mass showed mixture of sheets and Homer-Wright rosettes composed of small round cells [Figure 1a]. Immunohistochemistry revealed that the tumor cells showed diffuse membranous and cytoplasmic expression of CD99 [Figure 1b], and diffuse nuclear NKX2.2 expression with strong intensity [Figure 1c]. Papanicolaou staining of touch imprint smears of the lesion showed a well dispersed uniform population of small round cells [Figure 1d]. In immunocytochemistry, the tumor cells showed diffuse cytoplasmic expression of CD99 [Figure 1e]; diffuse nuclear expression of NKX2.2 with strong intensity [Figure 1f].
(a) Fluorescence in situ hybridization using dual-color probe for EWSR1 region (orange) and FLI1 region (green). A tumor cell of touch imprint smear showing one fused, one red and one green signal pattern. (b) Polyacrylamide gel electrophoresis of Reverse transcription polymerase chain reaction (RT-PCR) products. The present case showing a 166 bp band of type2 EWSR1/FLI1 fusion (lane 1). (Lane M: DNA marker, lane 2: Negative control, lane 3: Fusion transcripts of a skeletal Ewing sarcoma, a 130 bp band of type 1 EWSR1/FLI1 fusion), (c) Sequence analysis of the RT-PCR product of the present case. EWSR1 exon 7 fused to FLI1 exon 5
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F2
The touch imprint specimen revealed the presence of t (11;22) (q24;q12) translocation [Figure 2a]. Reverse transcription polymerase chain reaction (RT-PCR) using the removed tumor specimen could amplify the fusion transcript [Figure 2b], following sequence analysis revealed type 2 EWSR1/FLI1 fusion that involved EWSR1 exon 7 fused to FLI1 exon 5 [Figure 2c].