Primary localized amyloidoma of the renal pelvis: A case report and literature review.

Primary localized amyloidomas of the renal pelvis are challenging to diagnose, due to non-specific imaging results and the unusual location. The present study reports a rare case of primary localized amyloidoma of the renal pelvis and aims to illustrate the challenges in pre-operatively discriminating between this disease and transitional cell carcinomas. The present study identified that the mass was situated in the left renal pelvis using ultrasonography. A nephroureterectomy was performed following careful preparation. Finally, histopathological studies revealed that the tumor consisted of massive diffuse deposits of amyloid and microscopic amorphous eosinophilic material, which stained positively for Congo red, demonstrating potassium permanganate digestion. Consequently, a diagnosis of amyloid light chain-type amyloidoma was determined. Systematic examinations were performed following the unexpected diagnosis, which eliminated the possibility of amyloid associated-type amyloidoma. In total, 4 months post-surgery, the patient remained tumor-free.