Dermatologists are able to recognize most skin diseases based on their appearances, anatomic distributions, and behavior. Sometimes, however, those criteria do not allow a conclusive diagnosis to be made, and a skin biopsy is taken to be examined under the microscope or are subject to other molecular tests. That process reveals the histology of the disease and results in a specific diagnostic interpretation. In some cases, additional specialized testing needs to be performed on biopsies, including immunofluorescence,immunohistochemistry, electron microscopy, flow cytometry, and molecular-pathologic analysis.
One of the greatest challenges of dermatopathology is its scope. More than 1500 different disorders of the skin exist, including cutaneous eruptions ("rashes") and neoplasms(dermatological oncology deals with pre-cancers, such as an actinic keratosis; and cancers, including both benign masses, and malignant cancers- such as basal cell carcinoma,squamous cell carcinoma, and most dangerously, malignant melanoma). Non-cancerous conditions include vitiligo, impetigo, purpura, pruritus, spider veins, warts, moles, oral or genital herpes, chancre sores of syphilis, exposure to poison ivy and similar plants or other venom sources, rashes, cysts, abscesses, corns, and dermabrasions or cases dealing with wrinkles, peeling skin, or autoimmune attacks on the skin. Therefore, dermatopathologists must maintain a broad base of knowledge in clinical dermatology, and be familiar with several other specialty areas in Medicine.