Clear cell renal cell carcinoma with collecting duct carcinoma transformation: a case report and review of the literature

Collecting duct carcinoma (CDC), a rare and aggressive renal malignancy originating from the medullary collecting ducts, often presents with nonspecific symptoms and rapid metastatic progression, yielding a dismal prognosis. The occurrence of a composite CDC and conventional renal cell carcinoma is rare in the literature. We report a 55-year-old female with clear cell renal cell carcinoma with collecting duct carcinoma transformation in the same kidney. Seven months postoperatively, the patient developed metastasis to the lungs. A literature review of 18 mixed CDC with other tumors highlights metastatic propensity (52% cases) and poor outcomes, emphasizing the need for molecular profiling to guide targeted therapies. This report contributes to the growing body of literature regarding the complexity of composite renal malignancies, furthering our understanding of clinical, imaging, and histological findings of this rare phenomenon.