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 ≥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 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 1-2 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 3-5 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 mm clinical margins for low-risk lesions <2 cm
• Pathology review of margins essential

High-risk cSCC (see features above):

• Wider excision margins (6 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:

3. Refer all invasive melanoma to a specialist (dermatologist, plastic surgeon, or melanoma multidisciplinary team)
4. Sentinel lymph node biopsy: considered for Breslow >0.8 mm or with high-risk features; specialist decision
5. Staging imaging (CT or PET-CT): for Stage III/IV disease
6. 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 chronic condition management plan (GPCCMP; item 965): consider for patients with complex needs, including immunocompromised patients with multiple skin cancers requiring allied health input (e.g. lymphoedema physiotherapy, by direct referral under the plan) and practice nurse wound care
• 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 cm, perineural invasion, ear/lip location)
• Any lesion where the GP is uncertain of the diagnosis and biopsy is not immediately feasible