Metachronous Metastatic Renal Cell Carcinoma (RCC) to the Urinary Bladder: A Rare Cause of Hematuria.

Renal cell carcinoma (RCC) metastasis to the urinary bladder has been a rarely reported clinical entity, and its potential metachronous pathobiological process poses significant challenges in RCC therapy-transforming scenarios. In this case, we share the experience of a female patient who underwent radical nephrectomy in September 2020 and was on regular follow-up. In March 2022, she was found to have right pulmonary metastasis on PET-CT imaging and accordingly underwent right-sided wide local excision of the lung lesion by thoracoscopy in June 2022, which revealed metastatic clear cell RCC. She was kept on immunotherapy as discussed in the tumor board meeting and was followed up. Uncommonly, in November 2022, a bladder growth was found involving the left vesicoureteric junction on follow-up CT scan, due to hematuria occurring two years after nephrectomy. Histopathologic examination revealed this mass to be an RCC metastasis. The subsequent imaging diagnosis led to an aggressive treatment approach, resulting in cystectomy with anterior exenteration and ileal conduit. This case is unique in Bahraini literature, as it highlights the unpredictable patterns of RCC metastasis and the infrequent occurrence of the bladder as the site of such metastasis. This report attempts to dissect the intricacies of RCC metastases to the bladder by providing an accurate perspective on diagnosing and managing such atypical sites through a literature review and in-depth discussion of histopathological characteristics. It highlights the importance of an aggressive follow-up regimen for RCC patients, potentially irrespective of their primary site appearing well contained. It would add to our understanding of a broader spectrum of RCC metastatic disease.