Collision tumor of spindle cell lipoma arising from perirenal tissue and acquired cystic disease‐associated renal cell carcinoma: A rare case report

Abstract

Introduction Collision tumors are a rare phenomenon defined as two or more histologically distinct tumors that are in contact with each other. Case presentation The patient was a man with a history of end‐stage diabetic nephropathy under hemodialysis treatment for 15 years. A plain computed tomography scan showed a 4.3 cm mass with obscured margins in the right perirenal fat of the lower pole kidney. On T2‐weighted magnetic resonance imaging, the lesion showed heterogeneous signal intensity with a partially cystic component. A radical nephrectomy was performed. Histopathological and immunohistochemical examination revealed collision tumors constituted of a spindle cell lipoma covering the kidney surface underneath the perirenal fat and diffusely distributed acquired cystic disease‐associated renal cell carcinoma in the renal parenchyma. Conclusion We report the first case of collision tumors comprising spindle cell lipoma and acquired cystic disease‐associated renal cell carcinoma.

Keywords

• acquired cystic disease‐associated renal cell carcinoma
• collision tumor
• kidney
• spindle cell lipoma