Tumour seeding and upstaging in papillary renal cell carcinoma: an uncommon complication of renal mass biopsy.

The increased use of imaging has led to more frequent detection of small renal masses (SRMs), often prompting percutaneous renal mass biopsy (RMB) to guide management. While generally safe, RMB carries rare risks, including tumour seeding. We present a case of a 29 mm papillary renal cell carcinoma in a man in his 50s, where tumour seeding into the perinephric fat was identified along the biopsy tract following partial nephrectomy. This was associated with pathological upstaging and contributed to a decision for more intensive postoperative surveillance at the discretion of the multidisciplinary meeting. The case underscores the importance of careful patient selection for RMB, particularly in surgically amenable SRMs, where the risk of tumour seeding should be carefully considered.