Frequency of tumor induction in a thorotrast kidney

We have traced a group of 10 patients with Thorotrast kidney who underwent pyelography with Thorotrast in the early 1930s. An invasive carcinoma of the renal pelvis developed in 4 of them, diagnosed 21, 27, 32, and 34 years after Thorotrast pyelography. In 1 patient we found a carcinoma in situ of the renal pelvis after a latency of 35 years, and in 3 patients (35, 35, and 37 years after pyelography) the epithelium of the renal pelvis was dysplastic and metaplastic. Only in 2 patients of this group were no epithelial abnormalities found, after 24 and 25 years.