Figure 1. Gross specimen of the right
kidney: cut section of the kidney showing a heterogenous tumor showing
grey white homogenous area with whorling pattern (black arrow) and areas of necrosis and hemorrhage (red arrow).
Microscopically, the tumor was composed of spindle-shaped cells arranged
in interlacing fascicles, bundles, and whorls
(Figure 2). The tumor cells were
moderately pleomorphic with a moderate amount of eosinophilic cytoplasm,
oval to elongated nuclei, vesicular chromatin, and inconspicuous
nucleoli. Mitotic figures were frequent, constituting a 19/10 high power
field. Large areas of necrosis and hemorrhage were noted. The mass
involved the renal sinus and perirenal fat, however, Gerota’s fascia was
free of tumor. The lymphovascular invasion was noted. Extensive sampling
failed to reveal any epithelial component resembling renal cell
carcinoma. Microscopic examination of the inferior vena cava thrombus
revealed a tumor with similar morphology as in the kidney.