When cells in the adrenal cortex become abnormal, they can form non-cancerous, or benign, tumours called adrenal cortical adenoma. Sometimes cells in the adrenal cortex change and become cancerous. This type of cancer is called adrenocortical carcinoma.It is the most common cancerous tumour of the adrenal gland. Tumours can also start in the medulla of the adrenal gland. When chromaffin cells in the medulla become abnormal, they can lead to a tumour called pheochromocytoma.Most pheochromocytomas are non-cancerous, but some are likely to become cancerous.hen cells in the adrenal cortex become abnormal, they can form non-cancerous, or benign, tumours called adrenal cortical adenoma. Sometimes cells in the adrenal cortex change and become cancerous. This type of cancer is called adrenocortical carcinoma.