Part 1: Diagnosis. Differential diagnosis by site. Differential diagnosis by signs and symptoms. Diagnostic flowcharts. Part 2: Clinical features. Pathology. Part 3: Therapy. Guide to the main drugs used in the treatment of oral mucosal diseases. Main drug side effects of oral and perioral localisation. Therapeutic protocols. Part4: Biopsies and vital stains. How to perform a biopsy of the oral mucosa. How to perform a toluidine blue staining.