Burns and Skin Cancer

Burns

A burn is tissue damage from heat, electricity, chemicals, friction, or radiation. Because the skin's protection and thermoregulation depend on its layers, burn severity is described by depth:

• First-degree (superficial) burn: damages only the epidermis. The skin is red and painful but not blistered (like a mild sunburn). It heals in days without scarring.
• Second-degree (partial-thickness) burn: damages the epidermis and part of the dermis. It is red, painful, and blistered. Because some dermis (and its regenerating cells) survives, it usually heals, though deeper ones may scar.
• Third-degree (full-thickness) burn: destroys the entire epidermis and dermis, often reaching the hypodermis. The area may look white, brown, or charred and leathery, and is often painless in the center because nerve endings are destroyed. It cannot regenerate on its own and typically needs skin grafting.

Why extensive burns are dangerous. When a large area of skin is lost, two functions fail catastrophically: the barrier is gone, so the body loses fluid and electrolytes through the exposed surface (risking dehydration and shock), and microbes can invade (risking infection/sepsis). Thermoregulation is also impaired. This is why estimating the extent of a burn matters as much as its depth.

The rule of nines. To quickly estimate the percentage of body surface area (BSA) burned in an adult, the body is divided into regions each representing about 9% (or a multiple): each arm ~9%, the head ~9%, each leg ~18%, the front of the trunk ~18%, the back of the trunk ~18%, and the genital region ~1%. Adding the burned regions estimates total BSA, which guides fluid replacement and decisions about hospital or burn-center care. (Children's proportions differ — their heads are relatively larger — so pediatric charts are adjusted.)

Skin cancer

Most skin cancers arise from UV-damaged epidermal cells. The three main types, from most common/least dangerous to least common/most dangerous:

• Basal cell carcinoma: the most common; arises from the stratum basale. It grows slowly and rarely spreads, often appearing as a shiny or pearly bump. Highly treatable.
• Squamous cell carcinoma: from keratinocytes; can grow and spread more than basal cell if untreated, often appearing as a scaly, raised, or ulcerated lesion.
• Melanoma: from melanocytes; least common but most dangerous because it can spread (metastasize) early. Early detection is critical.

ABCDE — melanoma warning signs. A widely taught screening tool for suspicious moles:

• A — Asymmetry: one half doesn't match the other.
• B — Border: irregular, ragged, or blurred edges.
• C — Color: varied or uneven colors within the lesion.
• D — Diameter: larger than about 6 mm (a pencil eraser), though smaller ones can be melanoma.
• E — Evolving: changing in size, shape, color, or symptoms over time.

A mole showing these features should be evaluated by a clinician. Prevention centers on limiting UV exposure (sun protection, avoiding tanning beds) and regular skin checks.

How it works

Assessing a burn:

1. Depth: epidermis only (1st) → into dermis with blisters (2nd) → through dermis, leathery/painless (3rd).
2. Extent: apply the rule of nines to estimate %BSA.
3. Risk: large/full-thickness burns threaten fluid balance and infection → higher acuity.

Screening a mole: run through ABCDE; any concerning feature → clinical evaluation.

Comparisons

Common confusions

• Deeper isn't always more painful. Third-degree burns can be painless centrally because nerves are destroyed — a sign of greater severity, not less.
• Depth vs extent. Depth = how many layers; extent (rule of nines) = how much surface. Both matter.
• Basal cell vs melanoma. Basal cell is common and rarely spreads; melanoma is less common but the most dangerous.
• Rule of nines differs in children due to body proportions.

Memory aids

• Burn depth: "1st = red, 2nd = blistered, 3rd = leathery."
• ABCDE = Asymmetry, Border, Color, Diameter, Evolving.
• Rule of nines: arms 9, head 9, legs 18 each, front 18, back 18, groin 1.

Quick review

• Burn depth: first-degree (epidermis, red), second-degree (into dermis, blisters), third-degree (full-thickness, leathery, often painless, needs grafting).
• Extensive burns threaten fluid/electrolyte balance and infection; the rule of nines estimates %BSA burned.
• Main skin cancers: basal cell (common, rarely spreads), squamous cell (can spread), melanoma (least common, most dangerous).
• Screen moles with ABCDE (Asymmetry, Border, Color, Diameter, Evolving); prevent with sun protection.