Adrenal gland adenoma. Light micrograph of a section through an adrenal gland adenoma. Adenomas are benign (non-cancerous) tumours (neoplasms). The adrenal glands are located on the surface of the kidneys, and they release various hormones including adrenaline. Symptoms of adrenal gland tumours include excess hormone production that may lead to Conn's syndrome, which results in high blood pressure. Surgical removal of the tumours or even the whole gland is the only effective treatment. Magnification unknown.