Vol. 7, Issue 2, Part A (2025)

Renal sinus tumors are extremely rare and typically benign. Renal cell carcinoma (RCC) classically arises from kidney parenchyma and may extend intrarenally; however, it has never been reported to be entirely contained to kidney sinus. These tumors pose significant surgical challenges and carry high-risk complications due to their anatomical location. This case is the first reported example of a complete intrarenal sinus cystic RCC managed with a pioneering partial nephrectomy method.
A healthy male in his late 20s was in a follow-up for left renal stones, was found incidentally on imaging studies to have a 4 cm right Bosniak 4 cystic mass in the renal sinus yielding RCC as a leading diagnosis. The tumor was entirely surrounded by renal segmental vessels and collecting system structures. Given that the patient has renal stones in a relatively thin parenchyma contralateral kidney, radical nephrectomy was not recommended, and nephron-sparing surgery was considered essential.
Our novel trans-parenchymal surgical approach minimized the injury to the vascular and pelvi-calyceal system while allowing safe and complete enucleation of the tumor using artificial hydronephrocalycosis and intraoperative ultrasound. The kidney was successfully preserved, and histopathology examination confirmed the diagnosis of RCC. Follow-up CT scan after 6 months showed a perfectly normal kidney shape and size with no evidence of any tumor.
This case offers a hope for patients with anatomical challenges and high nephron preservation demands. It introduced a groundbreaking technique that could be a new standard for managing cases of intra-renal sinus tumors.