Which of the Following Statements About Hyperpituitarism Is Incorrect

Which of the following statements about hyperpituitarism is incorrect?

A) The commonest cause of hyperpituitarism is an adenoma, i.e., a benign tumour.
B) Results of pituitary tumours are due to excess hormone secretion.
C) Prolactinomas are uncommon pituitary tumours although they produce prolactin when they do occur.
D) Expansion of the tumour on surrounding tissues causes symptoms of raised intercranial pressure.