Dermatology training is pretty much limited to dermatopathology. Sure there are some practicing dermatologists out there that trained in both dermatology and pathology. I ,among them, but that is unusual. Even then, I do not feel the dermatologist is qualified to perform pathology, unless they have been routinely doing so. Though I completed an anatomic pathology residency, at this point I would not trust myself to read my brother's gastric biopsy.
On the other hand, many dermatologists are very qualified to read skin biopsies, i.e. dermatopathology. We are given lectures on skin pathology during residency training and it is a key part of Board examinations. Many dermatologists have taken extra training in dermatopathology fellowships. Curiously, nearly all dermatopathology fellowships are run by dermatologists, yet these training leaders bemoan the fact that less and less dermatologists are being propelled into that field. The last time I checked the ratio had gone from 50:50 to 70:30 in favor of pathologists.
One element that has soured the average practicing dermatologists on learning dermatopathology is governmental intervention in the form of the CLIA act. Dermatologists are no longer able to read their own slides, unless boarded in dermatopathology. Formerly, dermatologists could read their own slides, saving the health care system millions and millions of dollars, besides often providing better dermatology care ( it helps immensely to visualize the rash or lesion and correlate it clinically with its histology). Not so anymore.
One other point about pathologists reading skin slides> Some are very good at it and some mediocre. When I was a pathology resident there were some residents that loved derm path and others detested it. Most of those pathologists that went on to practice pathology, are forced to read derm slides. I am sure the ones who loved it back then, are good at it, while the others not so good.
In sum, I would trust a dermatologist who feels qualified to read dermatopathology slides, but let someone else do the regular histopathology.