Surgery chapters
Malignant skin tumours: BCC, SCC and melanoma
Basal cell carcinoma, squamous cell carcinoma and its precursors, Marjolin's ulcer, malignant melanoma (types, Breslow thickness, margins, sentinel node biopsy) and other skin cancers.
- BCC is the commonest skin cancer: slow, locally invasive, rolled pearly edge, almost never metastasises.
- SCC arises in sun-damaged skin, scars (Marjolin's ulcer) and immunosuppression; it has an everted edge and spreads to lymph nodes.
- Melanoma causes most skin-cancer deaths; Breslow thickness guides prognosis, margins and sentinel node biopsy.
On this page
Overview
Skin cancers are the commonest cancers in fair-skinned people, and ultraviolet (UV) radiation is the main cause. There are three main types:
- Basal cell carcinoma (BCC): commonest, slow, locally destructive.
- Squamous cell carcinoma (SCC): second commonest, can spread to lymph nodes.
- Malignant melanoma: less common but causes most skin-cancer deaths.
BCC and SCC are grouped as non-melanoma skin cancer.
Risk factors for skin cancer
- UV exposure (sunlight, sunbeds); fair skin, red hair, living near the equator.
- Ionising radiation; chemicals: arsenic, coal tar, aromatic hydrocarbons.
- Immunosuppression, especially organ transplant recipients (SCC rises sharply).
- Chronic scars and ulcers (SCC: burn scars, venous ulcers, osteomyelitis sinuses).
- HPV infection (SCC); smoking (SCC of the lip).
- Syndromes: xeroderma pigmentosum, Gorlin syndrome (BCC), albinism, familial atypical mole syndrome (melanoma).
Basal cell carcinoma (rodent ulcer)
Key facts
- Malignant tumour of the basal layer of the epidermis and hair follicles, so it occurs in hair-bearing skin.
- Most cases are between 40 and 80 years; more in men; almost only in white skin.
- Mostly on the face: around the eyes, nose and ears (the "mask" area).
- No known precursor lesion.
- Grows slowly and invades locally; metastasis is extremely rare.
Types
| Type | Features |
|---|---|
| Nodular / nodulocystic | Commonest (about 90%); pearly nodule with telangiectasia, later a central ulcer with a rolled edge |
| Superficial | Red scaly patch on the trunk; may be multifocal |
| Pigmented | Brown-black; can be confused with melanoma |
| Morphoeic (infiltrative) | Scar-like plaque with ill-defined edges; spreads widely under the skin, recurs often |
Histology: nests of basaloid cells with peripheral palisading of the outer cell layer.
A BCC is called a rodent ulcer because it slowly erodes deep structures, including cartilage and bone, if left untreated. Its edge is rolled and pearly with fine surface vessels.
High-risk BCC
- Larger than 2 cm.
- Near the eye, nose or ear (route to the skull).
- Recurrent tumour, immunosuppressed patient.
- Morphoeic, infiltrative or micronodular histology.
Treatment
- Surgical excision with a margin (usually a few millimetres, wider for ill-defined types) is the standard.
- Mohs micrographic surgery: staged excision with immediate microscopic checking of all margins. Best for high-risk sites (nose, eyelids), ill-defined or recurrent BCCs, as it saves normal tissue.
- Radiotherapy: useful in elderly or unfit patients; avoid in the young because of late radiation-induced cancers.
- Topical 5-fluorouracil or imiquimod: for biopsy-proven superficial BCC only.
An incompletely excised BCC recurs often and the recurrence is more aggressive, so involved margins need re-excision or Mohs surgery.
Precursors and in situ squamous lesions
| Lesion | Key points |
|---|---|
| Actinic (solar) keratosis | Rough scaly patch on sun-damaged skin; partial-thickness atypia; a minority turn into SCC |
| Cutaneous horn | Keratin projection taller than its base; about 10% have SCC at the base, so excise it |
| Keratoacanthoma | Fast-growing dome with a central keratin-filled crater; may heal on its own but looks like SCC, so excise |
| Bowen's disease | SCC in situ: slowly growing red scaly plaque; treat with 5-FU, imiquimod or excision |
| Erythroplasia of Queyrat | Bowen's disease of the glans penis |
Cutaneous squamous cell carcinoma
Key facts
- Malignant tumour of keratinocytes.
- Related to cumulative sun exposure; more in men and the elderly.
- Arises on sun-exposed skin (face, ears, lower lip, back of hands), in chronic scars and ulcers, and in immunosuppressed patients.
- BCC is about four times more common than SCC.
Clinical features
- Starts as an indurated nodule or plaque, often crusted; then ulcerates.
- The ulcer has an everted (heaped-up) edge, an indurated base and inflamed surrounding skin.
- Spreads to regional lymph nodes; the overall metastasis rate is low (about 2%) but higher in high-risk tumours.
Histology: invading sheets of squamous cells with keratin pearls; graded by Broders' grading (degree of differentiation).
High-risk SCC (worse prognosis)
| Factor | Higher risk |
|---|---|
| Size | More than 2 cm across |
| Depth | Thicker tumours (very thin ones rarely spread) |
| Grade | Poorly differentiated |
| Invasion | Perineural or lymphovascular invasion |
| Site | Lip and ear |
| Cause | Arising in burn scars, chronic ulcers, sinuses, irradiated skin |
| Host | Immunosuppression |
Marjolin's ulcer
A Marjolin's ulcer is an SCC that develops in a long-standing scar or chronic wound, classically an old burn scar, a chronic venous ulcer or an osteomyelitis sinus.
- Develops slowly, usually many years after the original injury.
- Classically painless, because scar tissue has few nerves.
- Lymph node spread is late at first, because the scar has few lymphatics; once it invades normal tissue it behaves aggressively.
- Any chronic ulcer that changes, bleeds or fails to heal should be biopsied (edge biopsy).
Marjolin's ulcer is the classic answer for "malignant change in a chronic burn scar or long-standing leg ulcer". It is usually an SCC.
Treatment of SCC
- Surgical excision gives histology and clearance. A margin of about 4 mm for tumours under 2 cm and about 1 cm for larger tumours.
- Mohs surgery for high-risk sites; radiotherapy for unfit patients or as an adjuvant.
- Palpable nodes: confirm (fine-needle aspiration) and perform block dissection.
- Most recurrences and node spread occur within 5 years, so follow-up is focused on that period.
BCC versus SCC
| Feature | BCC | SCC |
|---|---|---|
| Frequency | Commonest | Second |
| Precursor | None known | Actinic keratosis, Bowen's disease |
| Edge | Rolled, pearly, telangiectasia | Everted, indurated |
| Growth | Slow | Faster |
| Spread | Local invasion; metastasis extremely rare | Lymph nodes |
| Scar-related form | Rare | Marjolin's ulcer |
BCC Burrows (local), SCC Spreads (nodes).
Malignant melanoma
Key facts
- Cancer of melanocytes, so it can occur in skin, mucosa, the eye (retina/uvea) and meninges.
- Fewer than 5% of skin cancers but most skin-cancer deaths.
- Most melanomas arise in previously normal skin; only a minority (10–20%) start in an existing naevus.
Risk factors
- Intermittent, intense sun exposure and childhood sunburn; sunbeds.
- Fair skin, red hair, freckles.
- Many naevi or atypical naevi; giant congenital naevus.
- Personal or family history of melanoma.
- Immunosuppression; xeroderma pigmentosum.
Warning signs in a mole (ABCDE)
- Asymmetry
- Border irregular
- Colour variation
- Diameter increasing
- Evolution: change in size, shape, colour or height
Bleeding, itching, ulceration and satellite lesions are usually later signs.
Clinical types
| Type | Share | Features |
|---|---|---|
| Superficial spreading | Commonest (about 70%) | Flat, irregular lesion with long horizontal (radial) growth; a nodule means vertical growth has begun |
| Nodular | About 15% | Most aggressive common type; raised blue-black nodule; vertical growth from the start; trunk, head and neck; some are amelanotic |
| Lentigo maligna melanoma | 5–10% | Elderly, face and other chronically sun-damaged skin; long radial phase (lentigo maligna = Hutchinson's melanotic freckle) |
| Acral lentiginous | Rare in white skin; commonest type in dark-skinned and Asian people | Palms, soles and under the nail |
| Amelanotic | Uncommon | Skin-coloured; late diagnosis; may present as metastasis |
Subungual melanoma: Hutchinson's sign is pigment spreading onto the nail fold. Biopsy the nail matrix, not just the nail plate. A thin, regular dark stripe in a dark-skinned person is often benign racial melanonychia.
Pakistani patients are more likely to have acral lentiginous melanoma on the sole or nail bed, often mistaken for a fungal infection, wart or "non-healing ulcer" of the foot.
Diagnosis and staging
- Excision biopsy with a 2–3 mm margin and a cuff of fat. Avoid shave or punch biopsy of a suspected melanoma when complete excision is possible. Incision biopsy only for very large lesions (e.g. on the face).
- Breslow thickness: measured in millimetres from the granular layer of the epidermis to the deepest tumour cell. It is the most important prognostic factor for the primary tumour.
- Other adverse features: ulceration and high mitotic rate.
- AJCC TNM staging: T stage by thickness (T1 up to 1 mm, T2 1–2 mm, T3 2–4 mm, T4 more than 4 mm) and ulceration.
- Clark levels describe the anatomical level of invasion (epidermis to fat); now largely replaced by Breslow thickness.
Once nodes are involved, lymph node status becomes the most powerful prognostic factor in melanoma.
Treatment
Wide local excision margins (after diagnosis):
| Breslow thickness | Clinical margin |
|---|---|
| In situ | 5 mm |
| Less than 1 mm | 1 cm |
| More than 1 mm | 2 cm (wider margins add no benefit) |
Lymph nodes:
- Sentinel lymph node biopsy: a staging test for tumours thicker than 1 mm. It identifies the first draining node with dye and radioisotope. It helps staging but does not by itself improve survival.
- Clinically involved nodes: therapeutic lymph node dissection.
Advanced disease:
- BRAF V600 mutation is present in about half of melanomas: BRAF inhibitors (vemurafenib, dabrafenib) with a MEK inhibitor (trametinib).
- Immune checkpoint inhibitors: ipilimumab, nivolumab.
- Melanoma is relatively radio-resistant.
Prognosis
- Thin melanomas do very well after excision.
- Prognosis worsens with thickness, ulceration and mitotic rate.
- Once regional nodes are clinically involved, most patients already have hidden distant disease.
Other malignant skin tumours
| Tumour | Key points |
|---|---|
| Merkel cell carcinoma | Aggressive neuroendocrine tumour of the elderly; wide excision then radiotherapy |
| Kaposi sarcoma | Vascular tumour linked with HHV-8, HIV and transplant drugs; purple plaques and nodules; radiotherapy |
| Angiosarcoma | Highly malignant; can arise in chronic lymphoedema (lymphangiosarcoma) |
| Extramammary Paget's disease | Eczema-like patch in the perineum or axilla; may hide an underlying adenocarcinoma |
Expect: the rolled pearly edge, local invasion and very rare metastasis of BCC; Mohs surgery for high-risk facial sites; everted edge and nodal spread of SCC; Marjolin's ulcer in a burn scar or chronic venous ulcer; Bowen's disease as SCC in situ; keratoacanthoma with a central crater; superficial spreading as the commonest melanoma, nodular as the most aggressive, acral lentiginous on soles and nails in darker skin; Breslow thickness as the key prognostic factor; excision biopsy first; margins of 5 mm, 1 cm and 2 cm; and sentinel node biopsy for melanomas over 1 mm.
Quick revision
- UV radiation is the main cause of all three skin cancers.
- BCC: commonest; nodular type; rolled pearly edge; local spread only; excision or Mohs.
- SCC: everted edge; nodes; precursors AK and Bowen's; Marjolin's in scars.
- Keratoacanthoma: central keratin crater; excise because it mimics SCC.
- Melanoma: superficial spreading commonest; nodular most aggressive; acral in darker skin.
- Breslow thickness = granular layer to deepest cell; key prognostic factor for the primary.
- Excision biopsy 2–3 mm first; then wide excision 5 mm / 1 cm / 2 cm.
- Sentinel node biopsy for melanomas thicker than 1 mm (staging).
Written by The House Job from standard surgical references (Bailey & Love).
FAQ
Why is a basal cell carcinoma called a rodent ulcer?
Because it slowly eats into surrounding tissues, including cartilage and bone, like a gnawing rodent, even though it almost never spreads to distant sites.
What is a Marjolin's ulcer?
A squamous cell carcinoma arising in a chronic scar or wound, classically an old burn scar or a long-standing venous ulcer. Any non-healing or changing ulcer of this type should be biopsied.
What is the most important prognostic factor in melanoma?
For a localised primary tumour it is the Breslow thickness. Once regional lymph nodes are involved, nodal status becomes the strongest predictor.
When is sentinel lymph node biopsy offered in melanoma?
It is usually offered as a staging test for melanomas thicker than 1 mm without clinically involved nodes.
How should a suspicious pigmented lesion be biopsied?
By complete excision biopsy with a narrow 2–3 mm margin, so the pathologist can measure the full Breslow thickness.