Is pathology a four year residency or five? This depends. For the most typical of residents who wishes to become trained as a general hospital surgical oncologist who may also share responsibilities running the clinical lab, a combined AP/CP residency is a minimum. This is a four year residency with no required "credentialing year". The credentialing year was satisfied by doing either a preliminary medicine/surgery year, or by doing a special "surg path fellowship" year after your AP/CP basic training. This is not a board recognized fellowship but it is an extra year of increased responsibilities doing surg path full-time.
We do not need a fifth year to sit for the board certification exam. In the past, people who completed the fifth year surg path fellowship found it easier to pass the exam. Previously, some pathologists passed the boards without the surg path fellowship (since many did a non-pathology prelim year to satisfy their fifth year requirement). If you are very dedicated, you may sit for the AP/CP board exam at the end of four years, pass, and become a board certified pathologist.
But you probably couldn't get a job. Many institutions have grown accustomed to the high level of proficiency that the surg path fellowship brought to the applicant. It would be nearly impossible to get a job without doing a surg path fellowhip. So pathology training effectively is *still* five years. The difference is that motivated applicants can sit for their board exam after four years.
Many people will successfuly find jobs with AP/CP + surg path fellowship, but a lot of community institutions also want cytopathology experience. This requires an additional year fellowship to sit for the cytology board exam. Many folks want to do hemepath, pediatric path, immunoperoxidase, molecular path, derm path, neuropath, etc. This will require one or two additional years of training. So effectively, this means your training will become six to seven years.
It is possible to do shorter tracks, such as AP only, AP/neuropath, AP/dermpath, etc. By knocking off CP, you shave two years off your training but limit the types of employers who could hire you.
The take home message is that an AP/ residency is four years minimum, but five years effectively because of the surg path fellowship that employers are unwilling to give up. On top of that, you would add additional fellowships for specialty training.
This will remain true in all of the competitive and desirable job markets. It may be possible to get a job with AP/CP only if you worked in a less desirable location.
Good luck to all.