ESR1 and nonpapillary renal cell carcinoma: The diagnosis of ccRCC metastasis was substantiated by an immunohistochemical profile positive for PAX8, CAIX, and CD10, while negative for estrogen receptor, progesterone receptor, and HER2.<h4>Conclusion</h4>This case highlights breast metastasis as a rare but critical differential diagnosis in patients with a history of ccRCC, even decades after initial treatment.