LOW-GRADE SPINDLE-CELL CARCINOMA OF THE KIDNEY

The authors report a renal cell carcinoma composed largely of spindle cells of Fuhrman's nuclear grade II in which the bland appearance of t he cells and low mitotic index were reminiscent of a benign or low-gra de smooth muscle tumor. Keratin immunostaining was positive, but evide nce of epithelial differentiation was obtained by electron microscopy. The tumor was an incidental finding and it did not invade the periren al fat or the renal vein. Follow-up is only 24 months but the histolog ical features suggest that the prognosis may be better than that of a classic sarcomatoid renal cell carcinoma.