Pathophysiology
Clinical meaning
Mastery of standardized dermatological morphology is the foundation of all dermatological diagnosis. The NP must distinguish primary lesions (arising de novo in previously normal skin) from secondary lesions (resulting from evolution, manipulation, or treatment of primary lesions). Precise morphological description using standardized terminology enables pattern recognition for differential diagnosis, accurate documentation, and effective clinical communication. Primary flat lesions: Macule (<1 cm flat color change — e.g., freckle, petechia, vitiligo patch) and Patch (>1 cm flat color change — e.g., cafe-au-lait spot, tinea versicolor). Primary elevated solid lesions: Papule (<1 cm solid elevation — e.g., molluscum, verruca, dermal nevus), Plaque (>1 cm flat-topped elevation — e.g., psoriatic plaque, mycosis fungoides), Nodule (>1 cm deep dermal/subcutaneous mass — e.g., lipoma, cyst, BCC nodular type), Tumor (>2 cm solid mass). Primary fluid-filled lesions: Vesicle (<1 cm clear fluid — e.g., herpes simplex, varicella, contact dermatitis), Bulla (>1 cm clear fluid — e.g., bullous pemphigoid, burn, friction blister), Pustule (purulent content — e.g., folliculitis, acne, pustular psoriasis). Transient lesions: Wheal (edematous, evanescent, resolves <24 hours — urticaria; if individual wheals persist >24 hours, consider...