A Collision Tumor of Clear Cell Renal Cell Carcinoma and Clear Cell Papillary Renal Cell Tumor: A Case Report and Literature Review

Abstract Background Collision tumor refers to a special type of tumor in which two or more tumors of different origin occur in the same tissue or organ. There are few reports about primary renal collision tumor. We report a case of renal collision tumor composed of clear cell renal cell carcinoma (CCRCC) and clear cell papillary renal cell tumor (CCPRCT). Case presentation A 51-year-old woman who was initially hospitalized in the respiratory department because of cough and fever. Urinary computed tomography (CT) showed two different incidental masses in the right kidney. The patient underwent radical right nephrectomy without lymph node dissection and postoperative adjuvant treatment. Pathological results of surgical specimens showed that this was a collision tumor composed of CCRCC and CCPRCT. To the best of our knowledge, this is the first case in the world. No recurrence of local or distant metastasis was found in routine follow-up 14 months after the operation. Conclusions The coexistence of two kinds of renal malignant tumors is very rare. The microscopic features and immunohistochemical results of the tumors are helpful in the diagnosis of renal collision tumors composed of CCRCC and CCPRCT.