I personally would not withdraw from the pathology match.
First, the secret many medical students may not realize is that residents move from one field to another frequently. Surgery residents move to anesthesiology and EM, internal medicine residents move to pathology -- these are just a few examples I personally know of, and the movement happens even after just one year. So do not think of your matched residency as your life sentence. More flux exists than people realize.
Second, walking around with only an internship with the intent to scramble into a dermatology spot the following year is extremely risky, for several reasons...
(1) Image problem: Despite your stellar application, you may leave residents and attendings with the impression that you are disorganized because you didn't thoroughly investigate your options before matching as a medical student. What is worse is that they may think you had actually gone UNMATCHED as a medical student, even though this is not true, and you will labor under the bad impression that you were a subpar applicant, scores aside (we all know of high scoring creeps who didn't match). Remember that the interview process is complicated and competitive, and while on the trail, you are auditioning not just with your formally assigned interviewers, but also people whom you casually meet at dinner and during the day. Everyone has a say, big or small. So when you answer, "I'm a prelim/transitional right now," to the ubiquitous question, "And where are you from?" -- trust me, it will come out -- you'll need to go into your lengthy explanation to combat the common ugly thought that will pop into people's heads: "Ah, a prelim/transitional - this person didn't match the first time."
(2) Practically nonexistent scramble: Finding an open dermatology spot to scramble into as an MSIV is like finding water in the Sahara -- VERY RARE. Typically, those spots only happen if there were newly funded residency positions that were created during the application year, or if a program did not rank all their applicants because they too arrogantly assumed they would fill with their tippy top choices (and after a reported disaster several years back, that doesn't really happen anymore). If these spots do open up, they would go primarily to those dedicated unmatched applicants who slogged through the whole process from start to finish, not to folks flying in at the last minute, with no evidence of prior sacrifice to the Derm Gods. So who would those unmatched applicants be? Students from the department's own medical school, or those supported by aggressive, connected PDs who will quickly place strategic calls within the first few minutes of scramble. Such spots thus disappear FAST.
(3) Glide year stress: If you fail to scramble, then you are left high and dry with only an internship, and you would be forced into a position of either applying to those few very rare spots that open up for immediate start after your internship, or having a glide year which you need to fill with a dermatology fellowship -- positions ingeniously created by attendings to extract work from unmatched dermatology aspirants, and positions which themselves are notoriously difficult to land without the help of some inside angle. You would have to apply during that glide year, and undergo the same level of intense application stress while keeping up your fellowship work. And doing a fellowship does not guarantee matching: Notorious are the stories of fellows who apply multiple times, notching ever more fellowship years on their belt.
As for those very rare spots that open up during your internship? Same principles apply as mentioned in (2): These go to the poor souls who have assiduously cultivated their dermatology connections as medical students who did not match the first time around.
PATH IS GOOD: Apply from a position of strength. Match into a prestigious path residency. With your scores, you should have no problem getting into an MGH-type program. From there, you can spin your candidacy as someone who will excel at one of the lynchpins of dermatological diagnosis: the clinicopathological correlation (CPC). Although your path attendings may be disappointed, apply as a PGY1 since your pathology residency will have a schedule that allows you to tackle the intense derm interview process, and repay your coresidents by covering them after the season is over.
I don't think you have to go the path to dermpath route: You can spin it as you missed patient contact, and go directly into derm. Follow it up with dermpath. Dermies like derm-trained dermpaths. Then be in the position to make the most $/minute compared to any area of medicine under the sun.
