Collecting duct renal cell carcinoma: a single centre series and review of the literature.

Introduction: Collecting duct, or Bellini duct, renal cell carcinoma (CDRCC) is a rare tumour, comprising only 0.4-2% of all renal cell carcinoma. The goal of this study was to evaluate the cases in our institution and look at current available literature. Material and methods: We searched all data on renal cell tumours in our institution between 2011 and 2021 and identified four cases with confirmed CDRCC pathology. Important features were listed and analysed. We also reviewed current available literature and compared it to our case series. Results: All cases were men with a median age of 63.5 years. All were symptomatic at presentation. Two patients presented with flank pain and two with gross haematuria. Three patients had stage IV disease at time of presentation and one stage III disease. All cases had clear Bellini duct renal cell carcinoma appearance on microscopy with infiltrative tubular architecture and high-grade nuclear features. Immunohistochemic (IHC) staining was performed for diagnostic confirmation. Three patients underwent radical nephrectomy and received adjuvant chemotherapy. One case had kidney biopsy for diagnostic confirmation and received first line chemotherapy. Immunotherapy or tyrosine kinase inhibitor (TKI) were started for second, third or fourth line of treatment. Median overall survival after diagnosis was 11 months. Conclusions: CDRCC is a rare subtype of renal cell carcinoma with poor prognosis, typically presenting in a more advanced or metastatic stage. Diagnosis can be challenging. Multimodality treatment should be considered using radical surgery and systemic treatment.