Need more information to give a good answer. First off, how far along are you in your training? I assume you're a 3rd year if you're considering fellowships at this point, possibly 2nd. In either case, you have time to continue to improve your general surg path skills. Next, how adequate would you say your training is at your program in giving you exposure to AP? The only reason I would recommend doing a surg path fellowship over something subspecialized is either A) You're going to a "top" program (MGH, Stanford, JHU, etc.) compared to where you trained, so it significantly boosts your CV. B) You trained at Western Kentucky State or some other podunk program and you had subpar training with low volume/limited exposure to bread & butter AP. C) It's you're "in" to another fellowship that you really want to do and the institution offers you a two year package e.g. surg path + "X". Otherwise, a competent resident who came from a good or even above average program shouldn't need an extra year to feel comfortable.
Your mentor is giving the typical answer I would expect to come from academia which I would dispute on a couple of levels.
people with all around skills sets are more valued (i.e. general surg path),
It depends on where you go. If you go to a large academic institution or satellite lab where all you do is sign out GI, then they could give a rat's ass about your ability to differentiate atypical spindle cell lesions of the parotid on a stat FNA. However, in most private groups or academia with subspecialty + general sign out, then being the GI "expert" would be advantageous. Having all around skill sets is not bringing anything new to the table that everybody else doesn't already have in this type of setting. You will be expected to have this to some extent, even as a new grad. That's why you did four years of AP/CP.
residency doesn't train you adequately for signing out (too much new stuff and residency going from 5 to 4 years)
Bullcrap. A competent resident coming from a solid program should have received adequate training for signing out general AP. Yes, you won't know everything and there will be a learning curve after residency with some mistakes made along the way, but the mentality in our field that no one is ever ready; ergo, keep doing continuing fellowships is overblown. Also, the theory of less exposure because residency went from 5 to 4 yrs is false. When Pathology was 5 yrs; Residency = 1 yr Internship + 4 yrs Path. Those people who did a 5 yr residency back in the day weren't getting extra exposure to AP. They were doing rectal exams and writing scripts for kids with runny noses...That's why the ABP dropped the requirement of the intern year.
GI pathology is easy compared to the rest of surg path (i.e. derm, heme etc..).
Many old timers do feel that a GI path fellowship is useless because it consists of a high volume of total cases in the typical practice and the scope of pathologic differentials for what is most frequently encountered is not as broad as some other organ systems, so I get that. Also, when they trained, there was no such thing as a GI fellowship. So they might be thinking, "Why would anyone need a GI fellowship to sign out a bunch of colon polyps?" But, times are a changin'. Now that the fellowship has been created and graduates are out there, there are more private pathology groups who seek to have a GI path trained person to have a go-to-guy for difficult cases because they do such a high volume of them, and/or to market that person to gastroenterology groups to gain their business. In addition, some gastroenterologists are jumping on the bandwagon and prefer GI path fellows looking at their bxs. Hence why the pp owners you talked with recommended a GI path fellowship.
Ultimately, both can be valuable in certain circumstances as outlined above. But again, it depends on what your future goals may be along with your interests.
