Module 1: Dermatology - Primary Lesion Types

Macule

Flat lesion, not palpable, change in skin color only, <1 cm (example: freckles, petechiae, flat nevi)

Patch

Flat lesion, not palpable, ≥1 cm, may have very fine surface change (example: vitiligo, melasma)

Papule

Raised, solid, palpable lesion, <1 cm (example: wart, insect bite, molluscum)

Plaque

Raised, solid, palpable lesion, ≥1 cm, broad plateau-shaped rather than dome-shaped (example: psoriasis, seborrheic dermatitis)

Nodule

Solid, deep lesion, 1–2 cm, extends into dermis or subcutis and requires palpation of deep margin (example: lipoma, cyst, deep acne)

Tumor

Large solid mass, deeper than a nodule, benign or malignant

Vesicle

Fluid-filled lesion, <1 cm, small blister (example: herpes simplex, varicella)

Bulla

Fluid-filled lesion, ≥1 cm, large blister (example: bullous pemphigoid, pemphigus)

Wheal

Transient, itchy, edematous papule/plaque caused by superficial dermal edema; resolves within 24 hours (example: urticaria)

Pustule

Raised lesion containing purulent material (pus)

Cyst

Epithelial-lined sac in dermis or subcutis containing liquid or semisolid material (example: epidermoid cyst, pilar cyst)

Telangiectasia

Permanently dilated superficial blood vessels that blanch (example: rosacea, photodamage