Board review: lesion morphology and configuration
A high-yield vocabulary framework for describing lesions before naming a diagnosis.
Updated: 2026-09-13
Written for clinicians and medical students
This section is a teaching reference for doctors, residents and medical students. It is not patient guidance and not a substitute for clinical examination, and it must not be used for self treatment.
Primary lesions
- Macule and patch: flat colour change, separated at 1 cm. Papule and plaque: palpable elevation, separated at 1 cm [1].
- Vesicle and bulla: clear fluid, separated at 1 cm. A pustule contains purulent material; a wheal is transient dermal oedema [1].
- Nodule: a solid lesion extending deeper into dermis or subcutis. Cyst: an epithelial-lined cavity containing fluid or semisolid material.
- Board pearl: describe morphology, colour, surface, border, arrangement and distribution before forming the differential.
Secondary change and configuration
| Term | Diagnostic clue |
|---|---|
| Scale | Stratum corneum accumulation: psoriasis, dermatitis, dermatophyte infection |
| Crust | Dried serum, blood or pus: impetigo or exudative dermatitis |
| Erosion / ulcer | Partial / full-thickness epidermal loss |
| Lichenification | Thickened skin markings from chronic rubbing |
| Annular | Ring-shaped; examine the active edge and centre |
| Targetoid | Concentric zones; erythema multiforme is the classic association |