PMC3941948_01
Computed topography (CT) of the abdomen. A, CT scan images showed a huge lobulated cystic-solid tumor occupying the perirenal space of right kidney. B, The coronal reconstruction image showed a shadows of multiple tortuous vessels at the margin of huge mass.
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F1
A subsequent computed topography (CT) of the abdomen showed a huge lobulated cystic-solid tumor occupying the perirenal space of right kidney without evidence of either local invasion or lymphadenopathy (Figure  1).
Gross morphology. The tumor was firm and showed a yellowish white to tran-gray, myxoid and lobulated cut surface with prominent hemorrhage and necrosis.
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F2
The tumor was firm and showed a yellowish white to tran-gray, myxoid and lobulated cut surface with prominent hemorrhage and necrosis (Figure  2).
Microscopic features. A &B, Hyperchromatic and pleomorphic spindled cells surrounding staghornlike blood vessels (A,x100 original magnification; B, x200 original magnification. C, Tumor giant cells (arrow, x400 original magnification). D, Abnormal mitoses (arrow, x1000 original magnification). E, Tumor necrosis (N) (x200 original magnification). F, sporadic mature adipose tissue (x400 original magnification). Adipose cells showed S-100 immunostaining (inset, x400 original magnification). G, Storiform arrangements of spindle cells in fibrous stroma containing dense collagen fibers (x400 original magnification). H, Haphazard arrangements of multinucleated floret-like cells in a loose myxoid stroma (x400 original magnification).
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F3
The area consisted of hyperchromatic and pleomorphic spindled cells surrounding staghornlike blood vessels (Figure  3A, B). Tumor giant cells (Figure  3C) and abnormal mitoses (Figure  3D) were occasionally seen. Tumor necrosis were evidently present (Figure  3E). We also find sporadic mature adipose tissue (Figure  3F). The remaining 20% was characterized by haphazard, storiform or short fascicular arrangements of spindle cells in a loose myxoid to fibrous stroma containing dense collagen fibers (Figure  3G, H).
Immunohistochemical staining. Left panel, the lesion showed diffusely strong CD34 (A), CD99 (C), Bcl-2 (E) staining and an 85% Ki-67 proliferative index (G) (x200 original magnification). Right panel, the other lesion showed diffusely negative CD34 (B), positive CD99 (D), positive Bcl-2 (F) staining and a 20% Ki-67 proliferative index (H) (x200 original magnification).
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F4
Immunohistochemically, the tumor mostly showed diffusely strong CD34 (Figure  4A), CD99 (Figure  4C), Bcl-2 (Figure  4E) and vimentin staining.