Skin Cancer: Identification, Diagnosis, Management and Referral

Definition / Overview

Skin cancer is the most commonly diagnosed cancer in Australia. The three main types encountered in general practice are:

• Basal cell carcinoma (BCC): most common; arises from basal keratinocytes; low metastatic potential
• Cutaneous squamous cell carcinoma (cSCC): second most common; arises from keratinocytes; higher metastatic potential than BCC; can arise from premalignant lesions
• Melanoma: least common of the three but highest mortality; arises from melanocytes

Premalignant conditions seen in general practice include actinic (solar) keratoses (AKs) and Bowen disease (cSCC in-situ).

The GP is the primary point of triage for the vast majority of skin lesions in Australia. Early detection and appropriate management or referral are core competencies.

Pathophysiology / Risk Factors

Ultraviolet Radiation (UVR) as the Central Driver

• Cumulative UV exposure drives keratinocyte mutations, particularly in TP53, NOTCH1/2, CDKN2A, and NRAS
• Intermittent intense UV exposure (sunburns) is more strongly linked to BCC and melanoma
• Chronic cumulative UV damage has a clearer correlation with cSCC

Shared Risk Factors Across Skin Cancers

Clinical Features and Diagnosis

Actinic Keratoses (AKs)

• Rough, scaly papules or plaques on sun-damaged skin; may be white, yellow, red, or pigmented
• Often easier to palpate than visualise; feel like sandpaper
• Some become hyperkeratotic; cutaneous horns may develop
• Multiple confluent AKs in a sun-damaged field = field cancerisation
• Usually diagnosed clinically and on dermoscopy
• Biopsy indicated if an AK becomes tender, rapidly enlarging, ulcerates, or fails to respond to treatment (to exclude cSCC)
• Malignant transformation of a single AK is rare ($\approx 0.1\%$); however, patients with $\geq 10$ AKs have approximately 10% lifetime risk of developing cSCC

Bowen Disease (cSCC In-Situ)

• Well-defined, erythematous, scaly plaque; can resemble eczema or psoriasis
• Full-thickness epidermal dysplasia without dermal invasion
• May progress to invasive cSCC if untreated

Basal Cell Carcinoma (BCC)

• Nodular (most common): pearly, translucent papule or nodule with rolled borders and telangiectasia; may ulcerate centrally ("rodent ulcer")
• Superficial BCC: erythematous, scaly patch; may resemble eczema; common on trunk
• Morphoeic/sclerosing BCC: flat, scar-like, ill-defined; highest risk of incomplete excision
• Pigmented BCC: may resemble melanoma; blue-grey/brown pigmentation
• Slow-growing; rarely metastasises; but can cause significant local destruction if neglected

Cutaneous Squamous Cell Carcinoma (cSCC)

• Firm, hyperkeratotic nodule or plaque; may ulcerate
• Arising on a background of sun-damaged skin, chronic AKs, or Bowen disease
• Higher-risk features requiring urgent referral:
• Rapidly growing or enlarging
• Diameter $> 2\,\text{cm}$
• Poorly differentiated on histology
• Perineural or lymphovascular invasion
• Located on ear, lip, or within a scar
• Immunocompromised patient
• Recurrent lesion

Melanoma

• Superficial spreading: most common; flat or slightly raised; ABCDE changes
• Nodular: fast-growing, often amelanotic or dark; most dangerous subtype at presentation
• Lentigo maligna / lentigo maligna melanoma: slow-growing macular pigmentation on chronically sun-damaged skin of elderly patients; common on face
• Acral lentiginous: palms, soles, subungual; may occur in people with darker skin tones

ABCDE criteria for clinical assessment:

Investigation and Dermoscopy

Dermoscopy in General Practice

Dermoscopy significantly improves diagnostic accuracy for pigmented lesions. GP registrars should have basic competency:

• Melanocytic vs non-melanocytic: look for melanocytic structures (pigment network, dots, globules, streaks) vs non-melanocytic features (milia-like cysts in seborrhoeic keratoses; leaf-like structures in BCC)
• BCC dermoscopy: arborising telangiectasia, blue-grey ovoid nests, shiny white areas, spoke-wheel structures
• AK dermoscopy: strawberry pattern (red pseudo-network with hair follicle openings); surface scaling
• Melanoma red flags on dermoscopy: atypical pigment network, regression structures (white scar-like areas, blue-grey peppering), irregular dots/globules, atypical vascular pattern

When to Biopsy

• Excision biopsy: preferred for pigmented lesions suspected of melanoma; complete excision with $1\text{-}2\,\text{mm}$ margins
• Shave or punch biopsy: acceptable for BCCs, cSCCs, or when diagnosis uncertain; avoid shave biopsy for suspected melanoma
• Incisional biopsy acceptable only when a lesion is very large and full excision not feasible at initial visit

Management

Actinic Keratoses

Step 1: Photoprotection always - Broad-spectrum SPF 50+ sunscreen, sun-protective clothing, behavioural change - Consistent photoprotection reduces AK burden and risk of cSCC

Step 2: Lesion-directed treatment

Combination and sequential therapy is often used for field cancerisation.

Bowen Disease

• Cryotherapy, curettage, topical 5-FU, or imiquimod
• PDT particularly effective for large lesions
• Refer if diagnosis uncertain or lesion on face/genitalia

Basal Cell Carcinoma

Low-risk BCC (small, nodular, well-defined, primary lesion on trunk/limb): - Surgical excision with $3\text{-}5\,\text{mm}$ clinical margins: treatment of choice - Curettage and electrodesiccation: for small, low-risk superficial BCCs - Topical imiquimod or 5-FU: PBS-listed for superficial BCC only; appropriate when surgery is not feasible

Higher-risk BCC (morphoeic, large, facial, recurrent, or in high-risk sites such as H-zone of face): - Mohs micrographic surgery: gold standard for tissue-sparing, highest cure rate; refer to dermatologist or Mohs surgeon - Radiotherapy: elderly patients or those unable to undergo surgery

Advanced / metastatic BCC: - Hedgehog pathway inhibitors (vismodegib, sonidegib): specialist-initiated; PBS-listed for locally advanced or metastatic BCC - Immunotherapy (cemiplimab): when hedgehog inhibitors have failed

After first BCC: approximately 30-50% of patients will develop another keratinocyte cancer within 5 years. Advise regular self-skin checks and ongoing photoprotection.

Cutaneous Squamous Cell Carcinoma

Low-risk cSCC: - Surgical excision with $4\,\text{mm}$ clinical margins for low-risk lesions $< 2\,\text{cm}$ - Pathology review of margins essential

High-risk cSCC (see features above): - Wider excision margins ($6\,\text{mm}$ or more); Mohs surgery for head and neck - Refer to specialist: dermatologist, plastic surgeon, or head and neck surgeon - Consider sentinel lymph node biopsy and/or imaging in high-risk cases - Radiotherapy as adjuvant or for inoperable disease - Cemiplimab (anti-PD-1): PBS-listed for locally advanced or metastatic cSCC not amenable to surgery or radiotherapy (specialist-initiated)

Immunocompromised patients (organ transplant, haematological malignancy): - Increased frequency of skin surveillance (at least 6-monthly) - Lower threshold for biopsy and treatment - Refer to dermatologist for co-management

Melanoma

Confirmed or suspected melanoma on biopsy:

1. Do not perform staged excision in general practice without histological confirmation
2. Once confirmed on excision biopsy, re-excise with definitive margins based on Breslow thickness:

1. Refer all invasive melanoma to a specialist (dermatologist, plastic surgeon, or melanoma multidisciplinary team)
2. Sentinel lymph node biopsy: considered for Breslow $> 0.8\,\text{mm}$ or with high-risk features; specialist decision
3. Staging imaging (CT or PET-CT): for Stage III/IV disease
4. Adjuvant therapy (immunotherapy: nivolumab, pembrolizumab; targeted therapy: BRAF/MEK inhibitors for BRAF-mutant melanoma): oncologist-initiated, PBS-listed

Complications and Special Considerations

Field Cancerisation

• Multiple AKs on a background of chronic UV damage represent a "field" at high risk
• Treat the field, not just individual lesions
• Patients with field cancerisation require ongoing surveillance: 6-12 monthly skin checks in general practice

Immunosuppressed Patients

• Organ transplant recipients: cSCC risk is 65-100 times that of the general population; BCC risk is also markedly elevated
• Consider referral to dermatology for formal surveillance program
• Advise about strict photoprotection from time of transplantation

Perineural Invasion and Recurrence

• Perineural invasion in cSCC or BCC indicates high-risk disease
• Requires specialist management; adjuvant radiotherapy often considered

Psychological Impact

• Diagnosis of skin cancer, particularly melanoma, carries significant psychological burden
• Consider GP Mental Health Treatment Plan (MBS item 2715) for patients with adjustment disorder or anxiety following diagnosis

Long-Term Care, Surveillance, and Prevention in General Practice

Surveillance After Treatment

MBS Items Relevant to Skin Cancer in General Practice

• MBS Item 31355: Excision of skin lesion and repair (varies by size and site)
• MBS Item 30071 / 30072: Skin lesion destruction (cryotherapy, curettage)
• GP Management Plan (Item 721) / Team Care Arrangement (Item 723): consider for patients with complex needs, including immunocompromised patients with multiple skin cancers requiring allied health input (e.g., wound care nurses, lymphoedema physiotherapy)
• 75+ Health Assessment (Item 703): opportunistic skin check as part of the annual health assessment for older patients, who carry the highest burden of AKs, BCC, and cSCC

Prevention and Patient Education

• Broad-spectrum SPF 50+ sunscreen applied daily (not just beach days)
• Sun-protective clothing: UPF 50+ where possible
• Avoid peak UV hours (10 am-2 pm standard time)
• No sunbed use
• Regular self-skin examination monthly; know what is new or changing
• Educate patients that after one skin cancer, risk of another is significantly elevated

Aboriginal and Torres Strait Islander Health

• Skin cancer incidence is lower in Aboriginal and Torres Strait Islander people due to higher melanin content providing some UV protection; however, skin cancers do occur and may present at more advanced stages
• Acral lentiginous melanoma may occur on palms, soles, and subungual areas and can be missed
• Ensure culturally safe skin examination; consider gender concordance for full skin checks
• Close the Gap PBS co-payment scheme supports access to treatments including topical therapies

Key Red Flags Requiring Urgent Referral

• Any lesion suspicious for melanoma
• Rapidly enlarging, ulcerated, or bleeding lesion
• cSCC in immunocompromised patient
• High-risk cSCC features (size $> 2\,\text{cm}$, perineural invasion, ear/lip location)
• Any lesion where the GP is uncertain of the diagnosis and biopsy is not immediately feasible