When histological and immunohistochemical findings compatible with RMC are found, but the patient’s sickle cell trait status is unknown, hemoglobin electrophoresis can be performed to detect hemoglobin S. If hemoglobin S is not found and no other hemoglobinopathies are present, the tumor is classified as unclassified renal cell carcinoma (RCC) with medullary phenotype and SMARCB1 deficiency (6). The gene discussed is SMARCB1; the disease is hemoglobinopathy.