How often does medical malpractice happen?

Medical malpractice actually occurs very frequently, but wether or not the instance causes enough damage to entice the injured patient to sue is another thing entirely. For instance, a patient may have the flu that goes undiagnosed but in all likelihood, the patient will just get better on his or her own. But if something like cancer is misdiagnosed, the damage is going to be much more severe and the likelihood of a lawsuit is much greater.