Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 61 1 2023 03 07 61 63 Mazaher Ramezani Molecular Pathology Research Center, Imam Reza Hospital, Kermanshah University of Medical Sciences, Kermanshah, Iran. AND Clinical Research Development Center, Imam Reza Hospital, Kermanshah University of Medical Sciences, Kermanshah, Iran Kimia Karami Molecular Pathology Research Center, Imam Reza Hospital, Kermanshah University of Medical Sciences, Kermanshah, Iran . AND Clinical Research Development Center, Imam Reza Hospital, Kermanshah University of Medical Sciences, Kermanshah, Iran Kaivan Mohammadi Molecular Pathology Research Center, Imam Reza Hospital, Kermanshah University of Medical Sciences, Kermanshah, Iran. AND Clinical Research Development Center, Imam Reza Hospital, Kermanshah University of Medical Sciences, Kermanshah, Iran Farideh Baharzadeh Molecular Pathology Research Center, Imam Reza Hospital, Kermanshah University of Medical Sciences, Kermanshah, Iran. AND Clinical Research Development Center, Imam Reza Hospital, Kermanshah University of Medical Sciences, Kermanshah, Iran 2020 11 26 2023 01 15 Oncocytoma is a common benign kidney tumor. The size is often less than 5 cm. Oncocytomas may be misdiagnosed in clinic, radiology and histopathology for renal cell carcinoma. Different panels of immunohistochemistry (IHC) are suggested in the renal tumors with eosinophilic granular cytoplasm including oncocytoma, chromophobe and clear renal cell carcinoma. Here we report a large oncocytoma in a 64-year-old lady, that the mimickers ruled out by IHC. https://acta.tums.ac.ir/index.php/acta/article/view/8969