Extrarenal papillary renal cell carcinoma without a renal primary: a case report.

Introduction and importance: Primary extrarenal papillary renal cell carcinoma (pRCC) without an identifiable renal lesion is exceedingly rare, with fewer than ten cases reported in the literature. From a surgical standpoint, it poses a dual challenge: establishing an accurate diagnosis and determining the extent of resection in the absence of a renal primary lesion. Case presentation: We report the case of a 77-year-old male who was diagnosed with a solitary retroperitoneal extrarenal mass, confirmed by histopathology as a type 2 pRCC. He underwent laparoscopic resection of the mass; however, early postoperative follow-up demonstrated disease progression with pulmonary lesions. Systemic immunotherapy was initiated with nivolumab, achieving a partial response at the 3-month follow-up and stable disease at 12 months. Clinical discussion: Given the limited number of reported cases, the optimal management of extrarenal pRCC remains unclear. This case supports the potential role of immunotherapy and highlights the diagnostic and therapeutic challenges of such rare presentations. Conclusion: Extrarenal pRCC is a rare and challenging diagnostic entity. Multidisciplinary evaluation - including contrast-enhanced imaging, pathology, and surgical and medical oncology - is essential for accurate management. Immunotherapy may represent a therapeutic option in selected cases.