Late Recurrence of Renal Cell Carcinoma in Unusual Sites 23 Years After Nephrectomy.

Renal cell carcinoma (RCC) is a common malignancy in the elderly population and it is notorious for its mechanism of late metastasis to unusual anatomical sites. Late recurrences are common following curative treatment, such as radical nephrectomy. Pancreatic metastases and hepatic metastatic lesions make the diagnosis and classification of a primary tumor challenging. This necessitates a high index of suspicion and an extensive interrogation. We present the case of a 68-year-old Hispanic female with progressive pain in the right upper quadrant, weight loss, and decreased appetite. She has a history of renal cell carcinoma treated with radical nephrectomy and radiotherapy. A pancreatic biopsy was performed based on the ultrasound and computed tomography findings at a private clinic. Subsequently, the patient was referred to the Instituto Oncologico Nacional (ION) due to immunohistochemical features suggestive of a well-differentiated neuroendocrine tumor. At ION, a more comprehensive medical history was obtained, and the immunohistochemistry panel was extended, confirming the diagnosis of late recurrence of RCC. One possible explanation for the very late relapse of our patient is the presence of malignant cells that were spared or seeded during the surgical intervention and remained dormant or latent, subsequently spreading via hematogenous dissemination or via the lymphatic system. We highlight the importance of medical history, pathological examination, and immunohistochemical analysis in establishing a differential diagnosis, given the nature of RCC, which can often present asymptomatically and has a propensity for late recurrence. Further research should focus on developing standardized surveillance protocols for such cases.