What is a skin lesion?
In dermatology, a skin lesion refers to any visible or palpable change in the normal appearance of the skin. The term is neutral: a lesion may be benign (acne, a common mole, eczema) or may require medical evaluation (a lesion suspected of being cancerous, a severe infection). Learning to name and classify lesions is useful for describing what you observe to your doctor, for monitoring the progression of a condition, and for quickly identifying warning signs. Conventional dermatology distinguishes several major categories, grouped into primary lesions (initial appearance) and secondary lesions (development from a primary lesion).
How are lesions classified as primary and secondary?
This dermatological classification provides a framework for diagnosis:
- Primary lesions: present from the outset, directly reflecting the pathological condition (macules, papules, vesicles, blisters, nodules, pustules);
- Secondary lesions: result from the progression of a primary lesion or from associated phenomena (crusts, erosions, ulcerations, atrophy, lichenification, scars);
- A single condition may involve several types simultaneously: for example, psoriasis, which presents as an erythematous-squamous plaque (a combination of several lesions);
- The location (face, skin folds, palms, scalp), timing, andcourse of the condition round out the description to guide the diagnosis.
What are the main primary lesions?
The six main categories to remember:
- Macule: a change in color without elevation or infiltration. Examples: café-au-lait spots, freckles, senile brown spots;
- Papule: a small, solid elevation less than 1 cm in size. Examples: early-stage eczema lesion, flat wart;
- Vesicle: a raised lesion containing clear fluid, less than 5 mm in size. Example: cold sore, chickenpox;
- Bull: a large vesicle (more than 5 mm). Example: severe sunburn, pemphigoid;
- Pustule: a raised lesion containing cloudy or purulent fluid. Example: inflammatory acne, folliculitis;
- Nodule: a firm, palpable lesion deeper than a papule. Example: sebaceous cyst, lipoma, erythema nodosum;
- Plaque: a flat raised lesion larger than 1 cm. Examples: psoriasis, chronic eczema.
What are secondary lesions?
They indicate the progression or healing of the condition:
- Scales: visible clusters of shedding keratinized cells. Example: psoriasis, pityriasis;
- Scab: a dry deposit formed by exudation and coagulation following a wound or a ruptured blister;
- Erosion: loss of superficial tissue limited to the epidermis; heals without scarring;
- Ulceration: a deeper loss of tissue extending into the dermis; leaves a scar;
- Fissure: a linear crack in the skin (heels, very dry hands);
- Atrophy: thinning of the epidermis or dermis (mature stretch marks, corticosteroid-induced skin thinning);
- Lichenification: grid-like thickening of the skin caused by chronic scratching;
- Scar: permanent repair tissue replacing the damaged tissue.
How do you identify a suspicious lesion?
The ABCDE rule is the standard educational tool for identifying suspicious pigmented lesions:
- A — Asymmetry: Can the lesion be folded in half symmetrically? Asymmetry is suspicious;
- B — Borders: irregular, jagged, or poorly defined = requires further evaluation;
- C — Color: presence of multiple shades (brown, black, red, white, blue) within the same lesion;
- D — Diameter: greater than 6 mm, especially if the lesion is new;
- E — Changes over time: changes in size, shape, color, itching, or bleeding—this is the most important criterion.
This rule does not replace a dermatological examination but helps withself-monitoring. Any lesion that meets one or more of these criteria warrants an immediate dermatological evaluation.
What tests allow for an accurate diagnosis?
Dermatologists have several diagnostic tools at their disposal:
- Directclinical examination, with the naked eye and a magnifying glass;
- Dermatoscopy: examination using a magnifying, illuminated device, essential for pigmented lesions;
- Skin biopsy: removal of tissue under local anesthesia for histological examination under a microscope;
- Patch tests: screening for contact allergens whena skin allergy is suspected;
- Mycological, bacteriological, or viral cultures when an infection is suspected;
- Blood tests in certain contexts (autoimmunity, systemic inflammation);
- Imaging (high-frequency skin ultrasound, MRI) for deep lesions;
- Digital photographic monitoring of lesions requiring observation—particularly useful for people with numerous moles.
When should you seek emergency care?
Several situations require prompt or immediate medical attention:
- A new or changing pigmented lesion (ABCDE criteria met);
- A wound that does not heal after 4 to 6 weeks;
- A lesion that bleeds spontaneously, oozes, or ulcerates;
- Blisters or extensive skin peeling (suspected severe drug-induced skin reaction: Stevens-Johnson syndrome, Lyell’s syndrome);
- Extensive ring-shaped lesion with mucosal involvement;
- Generalized rash + fever + deterioration in general condition;
- Involvement of the eyelids, genitalia, or skin folds;
- Any systemic symptoms (generalized hives, facial swelling, difficulty breathing, malaise): life-threatening emergency—call 15 or 112.
How can you monitor your skin on a daily basis?
- Performa monthly self-examination of your entire skin, ideally after showering, in front of a full-length mirror with a handheld mirror for hard-to-see areas (back, skin folds, scalp, feet);
- Take photos of numerous or atypical moles to monitor their changes;
- Use SPF 50sunscreen daily, avoid sun exposure between 10 a.m. and 4 p.m., and wear protective clothing;
- Avoid tanning beds (classified as a Group 1 carcinogen by the IARC);
- Annual dermatological exam for people with fair skin, a personal or family history of skin cancer, or numerous moles;
- A skincare routine that respects the skin barrier: gentle cleansing, moisturizing, and a balanced diet rich in antioxidants;
- Manage stress, which can aggravate many chronic skin conditions;
- Always report any concerning skin lesion to a doctor, even if it is small.
