JP Morgan chief executive Jamie Dimon this week announced that he has been diagnosed with throat cancer. His email informing staff was notable for its openness about his treatment, the prognosis and potential consequences for the bank.

The US bank could easily have chosen to play its cards much closer to its chest. Apple, for example, was notably more guarded over chief executive Steve Jobs' battle with cancer. So what's the best approach when imparting grim tidings?