What are your challenges as a dermatopathologist?

There are several:

The Diagnosis:  The most critical challenge, day in and day out, is being correct about the diagnosis.  A person's life can hang on a diagnosis, and it is, understandably, a period of anxious waiting for the patient and the family until a diagnosis is determined with certainty.  The implications of a diagnosis are profound; whether a lesion is interpreted as melanocytic nevus or melanoma really matters.  Whether one's "rash" is a contact reaction or mycosis fungoides (a type of malignant lymphoma that can mimic a rash) has real implications for the patient.  When I evaluate every biopsy I consider it of the same importance as if it were a biopsy on my wife or me. The diagnosis is my principal role as a diagnostic dermatopathologist.

Writing and editing articles for the medical literature:  Writing is thinking, and thinking clearly about ideas of the natural history of disease is of critical importance for patients and physicians.  When writing an article for the medical literature, it is an attempt to describe one's experience with a disease and the implications that disease has for the patient.  Yet, when an article is published, it has the potential to affect the lives of millions of patients, now and in the future.  Thus, there is a very high bar for writing in the medical literature; writing must be done well, and it must be relevant.  I have had the delight of writing with many brilliant physicians over the years, and I have found it to enhance my ability to evaluate biopsies in the service of the diagnosis.
Teaching:  It is true that the teacher learns more than the student he teaches -- at least initially -- because he has to know the subject so well to be able to teach.  Students know a phony teacher immediately, especially if they are really students of a subject.  The best teachers challenge the core values of the student, and the best students challenge the core values of the teacher -- and move beyond the teacher.
Business:  It is often said today that medicine is a profession, not a trade or an industry.  I disagree profoundly with this premise.  It is a profession, but it is also a trade and an industry.  The reason American medicine became so diverse -- so specialized and encompassing so much territory in the fields of art, science, and technology -- is precisely because it was free politically to flourish as an industry until 1966; after this it was only semi-free because of the government encroachments of Medicare and Medicaid to this day.  We are coming to a point in American medicine, after the passage of the recent insurance regulation bill (in March of 2010) where the business of medicine is more and more difficult to conduct.  I will write more on this later, but suffice it to say for the purposes of this question, that if Americans want to maintain sub-specialities like dermatopathology (and a host of others), they should support political freedom with its consequence:  the free market.