Which of the following is most reliable feature of malignant transformation of pheochromocytoma –

The most definitive criteria for malignancy in pheochromocytoma is metastasis which is demonstrated by the presence of vascular invasion “Because benign and malignant pheochromocytomas may have an identical histological appearance, the only absolute criterion of malignancy is metastasis. “The diagnosis of malignant pheochromocytoma is made only when metastasis is demonstrated.”