Additional immunostaining was performed for chromogranin A, neuron-specific enolase, and synaptophysin to differentiate PHNEN from HCC and metastatic carcinoma.[6,10,29] The combination of histomorphological features and immunohistochemical results ultimately support diagnoses of PHNENs (Fig. 5).[30,31] Ki67 labeling index and mitotic grade indicate cellular proliferation are somewhat suggestive of malignant potential. The gene discussed is MKI67; the disease is metastatic carcinoma.