As surgical pathologists, we are excited by every case that comes before us because of the opportunity to make a diagnosis that matters to patients and clinicians. A correct diagnosis sets the patient and clinician along an appropriate treatment path. At the same time, there is an understanding that surgical pathology processes and laboratories are complex systems that offer ample opportunity to make mistakes. Errors occur for a variety of reasons. Some occur because of poor processes, some occur because of a lack of knowledge, some occur due to carelessness, and some occur because of external stresses. Trying to evaluate every possible source of error can be daunting. By breaking down the system into segments and evaluating each segment, errors can be more easily classified, analyzed, and addressed.