Prevalence of microscopic tumors in normal appearing renal parenchyma of patients with hereditary papillary renal cancer

Purpose: We describe the earliest renal lesions associated with hereditary papillary renal cancer and estimate the prevalence of microscopic papillary renal tumors. Materials and Methods. Grossly normal tissue was obtained from 12 kidneys d uring renal surgery in 9 patients with hereditary papillary renal cancer. T issue was examined microscopically and findings were compared to those prev iously reported to be associated with von Hippel-Lindau disease and sporadi c renal cell carcinoma. Results: A total of 92 microscopic papillary renal cell carcinoma lesions w ere identified on 46 of 88 slides (53%). No other lesions were identified. All tumors were solid and displayed the basophilic papillary histology char acteristic of hereditary papillary renal cancer. Extrapolation of the data predicted the prevalence of 1,100 to 3,400 microscopic papillary tumors in a single kidney in a patient with hereditary papillary renal cancer. Conclusions: The basophilic papillary histology characteristic of clinicall y apparent renal tumors in patients with hereditary papillary renal cancer also characterizes the multiple microscopic lesions seen in the kidneys. Th ese findings suggest that the earliest renal tumor in patients with an acti vating hereditary mutation of the met gene is papillary basophilic renal ca ncer. The large number of microscopic tumors in patients with hereditary pa pillary renal cancer was comparable to or greater than that seen in those w ith von Hippel-Lindau disease.