Villin--a marker of brush border differentiation and cellular origin in human renal cell carcinoma.

Expression of villin, a 95-kd F-actin bundling and severing protein, is restricted in animal tissues to epithelial cells with a brush border. Thus, the enterocytes of the intestine and epithelial cells of proximal but not distal tubules of the kidney are strongly positive. Here we report a similar staining pattern for human intestine and kidney. In four human colon adenocarcinomas villin expression was seen in tubular and glandular structures but not in the undifferentiated parts. Fourteen human renal carcinomas (9-Grade I and 5 Grade II) were villin-positive, and 2 sarcomatous renal carcinomas (Grade III) were villin-negative. The percentage of tumor cells that were villin-positive varied from 10-90% for the Grade I and II types. Our results indicate that villin may be a grading marker that deserves further study in renal carcinoma. They also raise the question whether the majority of renal carcinomas are derived from the proximal tubular epithelium rather than from the distal epithelium.