Academic pathology is small, and academic cytopathology is extremely small. Many good programs have internal candidates lined up or use their networks to recruit good candidates before they start interviewing random people. If it came to it, instead of reading your letters, I'd probably pick up the phone and call someone I know who knows you and get the real deal. If I can't find someone who knows who you are, then you'd drop to the bottom of my list and then I'd only read your letters carefully to look for red flags when I reached the bottom of my list.
Now, what I just told you is horrible but unfortunately horribly true and my only point is to tell you that the LOR doesn't really matter but to not have one from a cytopathologist implies you don't have an academic cytopathologist to advocate for you and that is what can make a big difference if you are a "random" applicant from a smaller program. It is a situation where doing an early away elective can help tremendously, because you can audition for a fellowship and also gain an advocate at that program.