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 urticarial vasculitis).
Secondary lesions: Scale (excess stratum corneum shedding — psoriasis: silvery micaceous; seborrheic dermatitis: greasy yellow; pityriasis rosea: collarette), Crust (dried exudate — honey-crusted: impetigo; hemorrhagic: ecthyma), Erosion (superficial epidermal loss, heals without scar — ruptured vesicle), Ulcer (loss through epidermis into dermis or deeper, heals with scar — venous stasis, arterial insufficiency, BCC/SCC), Fissure (linear crack — cheilitis, interdigital tinea), Excoriation (linear scratch mark — pruritic conditions), Lichenification (thickened skin with accentuated markings from chronic rubbing — chronic eczema), Atrophy (thinning — chronic corticosteroid use, lichen sclerosus), Scar (fibrous replacement of dermis).