Uromodulin as a radiographic mimicker of renal cell carcinoma recurrence after partial nephrectomy

Tamm-Horsfall protein (THP) is the most abundant protein in urine, yet its function remains incompletely understood. It has been hypothesized that THP contributes to the maintenance of urinary homeostasis. We report a case of a 71-year-old male with a history of renal cell carcinoma treated with partial nephrectomy in 2017. He represented 8 years later with an enlarging, enhancing renal mass concerning for recurrence. A radical nephrectomy was performed and revealed a benign specimen with a positive PAS stain, consistent with THP. To our knowledge this is the first report of THP deposition in the renal parenchyma after partial nephrectomy.