A Rare Case of Collecting Duct Carcinoma: A Comprehensive Analysis Using Ultrasound, Computed Tomography, and Histopathological Examination.

Collecting duct renal cell carcinoma (cdRCC) is an exceptionally rare and aggressive subtype of renal cell carcinoma, accounting for approximately 1% of all renal tumors. This case is notable due to the comprehensive use of multi-modality imaging and detailed histopathological examination, offering valuable insights into the diagnostic challenges and management of this rare condition. A 64-year-old male presented with progressive right flank pain, hematuria, and decreased urine output. Imaging studies revealed a hypoechoic lesion in the right kidney, predominantly located in the hilar and perihilar regions, suggestive of a malignant renal tumor. Further diagnostic evaluation, including a right radical nephrectomy, was performed. The histopathological examination of the resected tissue confirmed the diagnosis of cdRCC, characterized by a tubulopapillary growth pattern, significant pleomorphism, and sarcomatoid changes. Immunohistochemical analysis showed strong positivity for epithelial membrane antigen and CK7, confirming the aggressive nature of the tumor. This case underscores the importance of early diagnosis and a comprehensive diagnostic approach to managing cdRCC. Despite advances in imaging techniques, a definitive diagnosis often relies on histopathological and immunohistochemical analysis. The aggressive nature of cdRCC and its generally poor prognosis highlight the need for prompt and accurate diagnosis to potentially improve patient outcomes. This report adds to the limited literature on cdRCC, emphasizing the challenges and considerations in diagnosing and managing this rare form of renal carcinoma.