PMC5556985_01
CT imaging shows a heterogeneous partially calcified enhancing solid mass of the right kidney and gross findings show a necrotic and friable soft tissue mass involving the distal ureteric margin and the renal vein.
CRIU2017-1750694.001.jpg
PMC5556985_01_CRIU2017-1750694.001.jpg
fig1
Lesion is noted adjacent to and compressing the right renal artery with anteromedial displacement (Figure 1). Upon further dissection, the tumor was seen abutting the pelvis rather than invading it, although it did appear to obliterate the renal sinus (Figure 1).
Diffusely infiltrative small blue cell tumor, magnification (100x); round cells with scant cytoplasm and moderate degree of nuclear atypia, magnification (200x).
CRIU2017-1750694.002.jpg
PMC5556985_01_CRIU2017-1750694.002.jpg
fig2
Nephroblastoma, lymphoma, sarcomatoid renal cell carcinoma, and rhabdomyosarcoma were brought into the differential diagnostic considerations and were ruled out, and a diagnosis of renal PNET was offered (Figure 2).
Diffuse and strong membranous positivity for CD99, magnification (200x); diffuse and moderate nuclear positivity for FLI-1, magnification (200x).
CRIU2017-1750694.003.jpg
PMC5556985_01_CRIU2017-1750694.003.jpg
fig3
The histopathologic diagnosis was confirmed by immunohistochemistry with characteristic positivity for CD99 and FLI1 (Figure 3), as well as FISH studies documenting EWS gene rearrangement (Figure 4).
FISH studies: EWS gene rearrangement.
CRIU2017-1750694.004.jpg
PMC5556985_01_CRIU2017-1750694.004.jpg
fig4
The histopathologic diagnosis was confirmed by immunohistochemistry with characteristic positivity for CD99 and FLI1 (Figure 3), as well as FISH studies documenting EWS gene rearrangement (Figure 4).