Final answer:
If a medical assistant mistakenly opens personal mail addressed to the physician, they should apologize and not disclose or discuss the contents without permission.
Step-by-step explanation:
If a medical assistant mistakenly opens an item of incoming mail marked 'personal' and addressed to the physician, they should immediately apologize to the physician for the mistake and explain what happened. The medical assistant should not disclose or discuss any of the contents of the mail unless the physician gives permission to do so. It is important for the medical assistant to respect the privacy and confidentiality of the physician's personal mail.