Bellini Duct Carcinoma Misdiagnosed with UrothelialPapillary Carcinoma

Collecting (Bellini) duct carcinoma (CDC) or Bellini duct carcinoma (BDC) is a rare subtype of kidney tumors,accounting for less than 3% and known to have the worst prognosis. It is known to have multiple clinical presentations; this iswhy it can be easily misdiagnosed. The aim of this article is to present a case of CDC that was initially misdiagnosed withurothelial papillary carcinoma (UPC) in a 41-year-old male.Case Presentation. Our patient presented with a leftflank painevolving for one month and one episode of gross macroscopic hematuria. Upon presentation, he had left costovertebral angletenderness. Initial lab tests were normal. Computed tomography revealed a 5 cm solid mass of the left renal pelvis and multipleinfracentimetric perihilar lymph nodes. Subsequently, the patient had left nephroureterectomy. Microscopic examinationshowed the presence of a high-grade urothelial papillary carcinoma of the renal pelvis’lumen. All four of the dissected lymphnodes showed disease metastasis. Three years after establishing the diagnosis, the patient presented again for chronic abdominalpain, with a recent history of weight loss. CT scan showed a left paraaortic mass infiltrating the left psoas muscle over a lengthof 12 cm. Immunohistochemical profiling of this mass confirmed the diagnosis of Bellini duct carcinoma, rejecting the initialdiagnosis of UPC. Therefore, the patient required a cisplatin-gemcitabine-based chemotherapy regimen.Conclusion. BDCremains one of the rare aggressive subtypes of RCC, having a multitude of initial clinical presentations and an unfavorableprognosis. In this patient, CDC was masquerading as a transitional cell carcinoma that should always be kept in mind as apossible presentation. Corresponding early imaging and histopathology exams are primordial for a correct diagnosis and thus abetter prognosis