Your terminal patient has cognitive dysfunction from a closed head injury, and if his family pleads with you to keep him unaware of his terminal prognosis because of how he won't be able to deal with it, would you?
"I would only withhold information if the patient were not able to process it appropriately due to cognitive impairment and when such a situation would interfere with my care. The family may be right in predicting an ugly reaction, but if the patient's right to know doesn't interfere with my care, I owe the information to my patient."
"If my patient can understand the objective significance to the diagnosis, it's my duty to inform him or her, as a member of the 'partnership' we've established for care in the patient-physician relationship. Anything less is dishonest. Unless the patient had an Advanced Directive forbidding such bad news, and that is doubtful, I need to use my own judgement in when, how, and to what extent I keep my patient informed, tempered with what ability there is for him or her to fully understand."
This is a question centering on a patient's right to know. Keeping germane information of one's illness from him or her is deceit by omission. The issue gets cloudy, however, if a patient is not completely oriented. You should base your answers according to ethics and legality.
"If my patient is oriented to person, place, and time--the three cardinal perceptions--I owe it to him or her to be completely honest; by 'completely' I mean fully, without holding anything back."