MKI67 and pheochromocytoma: Correlation analysis showed a negative correlation between insulin gene enhancer protein 1 and tumor Hounsfield unit and a positive correlation between insulinoma-associated protein 1 and Ki67 proliferation index.<h4>Conclusions</h4>Insulinoma-associated protein 1, insulin gene enhancer protein 1, and secretagogin, which are second-generation neuroendocrine immunohistochemical markers, can be used in the differential diagnosis of pheochromocytoma.