PMC3921769_01
Abdominal CT scan with a right renal sinus mass showing heterogeneous enhancement.
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A subsequent CT scan demonstrated a 2.4 x 2.1 cm right renal cortical mass in the mid to upper pole that protruded into the renal sinus and showed heterogeneous enhancement (Fig. 1).
Encapsulated tumor, well demarcated from surrounding adipose tissue of the renal hilum (2A, x 20) with clusters of fat cells (arrow) between the vascular channels (2B, x 40) (H & E stain).
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Under low power examination, the lesion was well circumscribed and appeared encapsulated (Fig. 2a). Of interest was the presence of several clusters of fat cells distributed throughout the lesion (Fig. 2b).
Sinusoidal capillary-sized vessels lined by hobnail endothelial cells with intravascular fibrin thrombi (3A, x 200) and extramedullary hematopoiesis (3B, x 200). Note the spleen-like architecture of the tumor (H & E stain).
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The tumor was composed of dilated sinusoidal capillary-like vessels that were lined by hobnail endothelial cells with a mild degree of nuclear atypia (Fig. 3B). Fibrin thrombi and extramedullary hematopoiesis were easily identified in the lumen of the small vessels (Fig. 3a and 3b). In several areas, the architecture of the capillary-like vessels was reminiscent of splenic parenchyma (Fig. 3a).
Focal intravascular extension (x 40) (H & E stain).
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A small focus of intravascular extension was observed at the periphery of the tumor (Fig. 4).