Extensive Invasion of the Pelvicalyceal System Shortly After Combined Locoregional Treatment of Renal Cell Carcinoma: A Report of an Unusual Complication

Renal cell carcinoma (RCC) is a relatively common malignancy and is often diagnosed incidentally in imaging in early stages, where interventional radiologic techniques provide competent treatment options with minimal risk for major complications. A 72-year-old woman diagnosed with a 5 cm tumor of her right kidney in computed tomography (CT) with typical findings of RCC opted for percutaneous interventional treatment instead of surgical treatment. Transarterial embolization (TAE), followed by ultrasonographically guided microwave ablation (MWA), was performed with no immediate post-interventional complications. The patient returned 10 weeks post MWA with right flank pain and hematuria, and CT revealed almost complete necrosis at the original tumor site but also significant tumor extension in the upper calyces and pelvis of the right kidney. This was histologically confirmed after nephroureterectomy. The complication is thought to be unrelated to the TAE, and cell implantation potentially occurred due to calyceal penetration during antenna placements. TAE and thermal ablation are established techniques for managing locoregional disease. Urinary tract invasion by treatment-naive RCC has been reported in the literature; however, invasion of the pelvicalyceal system by RCC as a result of ablation should be considered an extremely unusual, unexpected, and severe complication, which impairs the prognosis.