Renal Cell Carcinoma Mimicking Transitional Cell Carcinoma: A Case Report.

BACKGROUND Preoperative differentiation between renal cell carcinoma (RCC) and transitional cell carcinoma (TCC) is of utmost important for determining surgical strategy, whether nephrectomy or nephro-ureterectomy, as well as the necessity for wider lymphadenectomy and subsequent intensive surveillance, as the latter is more prone to recurrence. CASE REPORT A 76-year-old Chinese woman presented with flank pain and gross hematuria, and was found to have right-sided hydronephrosis. An obstructing tumor in the renal pelvis was shown on a computed tomography (CT) intravenous pyelogram. Although its enhancement pattern was suggestive of RCC, the location within the collecting system without any attachment to the renal parenchyma is very unusual. The mass was diagnosed histopathologically as RCC on both ureteroscopic biopsy and subsequent radical nephrectomy. CONCLUSIONS We present a rare case of RCC growing exclusively in the renal pelvis, mimicking a TCC. Hypotheses regarding this unusual presentation include direct invasion, continuous implantation, and intraluminal transit down the collecting system. The characteristics on imaging studies, including greater enhancement and higher tumor-to-kidney attenuation ratio, may provide a clue for diagnosis, but ureteroscopy and histopathology are the criterion standards and should be considered as part of routine preoperative assessment. Amidst controversies and inconsistencies, more and more emerging evidence suggests that RCC with urinary collecting system invasion is associated with less favorable overall and recurrence-free survival, especially in localized diseases.