Misdiagnosis of pancreatic metastasis from renal cell carcinoma: A case report.

Background: Pancreatic metastases account for only a small proportion of all pancreatic malignancies. Isolated pancreatic metastasis from renal cell cancer (isPM-RCC) is extremely rare and may be difficult to differentiate from more common primary neoplasms. A history of nephrectomy is crucial for the diagnosis.

Case Summary: We report the case of a 64-year-old Asian man who was diagnosed with a mass in the pancreatic head using computed tomography. He had no related symptoms, and his medical history was unremarkable, except for unilateral nephrectomy performed to remove a "benign" tumor 19 years ago. All preoperative imaging findings suggested a diagnosis of pancreatic neuroendocrine tumor. However, ultrasound-guided biopsy revealed features of clear cell renal cell carcinoma (ccRCC). Re-examination of the specimen resected 19 years ago confirmed that he had a ccRCC. The pancreatic mass was resected and pathological examination confirmed isPM-RCC.

Conclusion: Misdiagnosis of isPM-RCC is common because of its rarity and the long interval from resection of the primary tumor and manifestation of the metastasis. The history of the previous surgery may be the only clue.