Intrarenal epidermoid cyst mimicking a cystic renal cell carcinoma: A case report and review of literature.

Key Clinical Message:This case highlights the diagnostic pitfalls that can occur when evaluating complex cystic renal masses. Distinguishing epidermoid cysts from renal cell carcinoma is difficult but imperative to guide conservative management when appropriate, avoiding unnecessary nephrectomy. Abstract:Renal epidermoid cysts are extremely rare, with only 12 cases reported in the literature. Their radiographic features often resemble cystic renal cell carcinoma, frequently prompting unnecessary nephrectomy. A 64-year-old man with a history of nephrolithiasis presented with left flank pain and hematuria. Imaging revealed a complex cystic renal mass suspicious for renal cell carcinoma. Following left radical nephrectomy, histopathology examination revealed a benign epidermoid cyst. Renal presentation of epidermoid cyst poses unique diagnostic and therapeutic challenges. Possible pathogenesis includes ectopic epidermal implantation during embryogenesis or squamous metaplasia following chronic irritation or deficiency. Radiographic distinction from concerning entities like renal cell carcinoma is difficult but imperative to avoid extensive surgery. This case highlights the diagnostic pitfalls and management considerations for renal epidermoid cysts. Additional study of clinical and imaging factors that distinguish epidermoid cysts from renal cell carcinoma can guide conservative management when appropriate, avoiding unnecessary nephrectomy for benign disease.