Analysis of solid renal dysplasia by flow cytometry: malignant potential?

Renal nodular blastema/nephroblastomatosis is a recognized precursor of Wilms tumor. It also has been shown that nodular renal blastemata are seen in association with dysplastic renal parenchyma secondary to obstructive uropathy (i.e., ureteroceles or ectopic ureters). In an attempt to improve our understanding of the critical relationship between renal dysplasia and neoplasia, we performed flow cytometric evaluation on 16 paraffin-embedded specimens of dysplastic kidneys removed during the period 1984-1989. All nephrectomy specimens were associated with obstruction, either duplex collecting systems (10), ectopic ureters (2) or posterior urethral valves (2), or vesicoureteral reflux (2). One specimen was found to contain nodular renal blastema. No evidence of malignancy was found in any specimen. A specimen of normal kidney and two of Wilms tumor (favorable histology) were studied for comparison. Nuclear deoxyribonucleic acid (DNA) ploidy studies were performed on single dissociated nuclei after deparaffinization and staining with propidium iodide. All dysplastic specimens, including the specimen with nodular renal blastema, demonstrated a diploid pattern of DNA as did the specimens of normal renal tissue. The Wilms tumor specimens demonstrated a diploid and a tetraploid pattern. In view of the fact that Wilms tumor may demonstrate diploid DNA patterns on flow cytometry, the findings of diploid patterns on all specimens of solid dysplasia militate against but do not eliminate the possibility of malignant degeneration.