How do I tell a solar keratosis from skin cancer?

Solar keratoses are rough, scaly, reddish-pink papules on chronically sun-damaged skin — they 'feel before they see': the sandpaper texture is often palpable before the lesion is prominent. BCC typically presents as a pearly, flesh-coloured papule with rolled edges, surface telangiectasia, and a tendency to bleed or develop a central ulceration — the classic 'rodent ulcer'. Superficial BCC is a flat pink plaque with a fine thread-like border, often on the trunk. SCC presents as a keratotic nodule, ulcerated plaque, or rapidly growing dome-shaped lesion. Any lesion that does not heal within four weeks, bleeds without trauma, or is growing should be assessed clinically with dermoscopy and biopsied if there is any uncertainty.

What is field cancerisation and why does it matter?

Field cancerisation describes a zone of chronically sun-damaged skin where the entire area contains UV-mutated keratinocytes — not just discrete visible lesions. This means multiple solar keratoses, in situ SCCs, and invasive skin cancers can arise and recur across the same anatomical region. Treating individual lesions in isolation (cryotherapy of each spot) is often insufficient. Field treatments that address the whole zone — topical 5-fluorouracil, imiquimod, diclofenac, or photodynamic therapy — are important adjuncts to managing field cancerisation, alongside strict sun protection and regular surveillance.

Which skin cancers need urgent specialist referral?

Urgently refer for specialist assessment: any suspected SCC (which can metastasise to lymph nodes if high-risk or neglected); high-risk BCC features — morphoeic or infiltrative subtype, recurrent, large, central face or H-zone involvement, ill-defined margins; any lesion with perineural symptoms (numbness, paraesthesia near the lesion); suspected lymph node involvement; lesions in immunosuppressed patients; and any suspected advanced or metastatic disease requiring systemic therapy. Vismodegib (for advanced BCC) and cemiplimab (for advanced SCC) are PBS Authority medicines requiring specialist initiation.

Is nicotinamide useful for skin cancer prevention?

Yes, in selected high-risk patients. The ONTRAC trial published in the New England Journal of Medicine in 2015 demonstrated a 23% reduction in new non-melanoma skin cancers in high-risk patients (two or more non-melanoma skin cancers in the preceding five years) taking nicotinamide 500 mg twice daily. Nicotinamide (vitamin B3, not to be confused with nicotinic acid niacin) is inexpensive and available over the counter. It is not PBS-subsidised but is a low-cost preventive option for high-risk patients, recommended alongside sunscreen and surveillance. Benefit does not persist after cessation.

How are transplant patients managed differently?

Organ transplant recipients are at approximately 65 times the SCC risk of the general population due to immunosuppression, particularly azathioprine combined with UV exposure. BCCs are also substantially more common and more aggressive. Management involves dermatology shared care with aggressive surveillance (three-monthly), use of topical chemoprevention (5-fluorouracil), modification of immunosuppression towards less skin-cancer-promoting agents where clinically possible (switching azathioprine to mycophenolate), and systemic acitretin for patients with multiple SCCs. Patients on voriconazole for fungal prophylaxis are at additional elevated SCC risk — switch to an alternative antifungal if NMSC develops.

Solar keratosis and non-melanoma skin cancer

Solar keratosis, BCC, and SCC: skin cancer in Australian general practice

By Dr HB Lo, FACRRM Reviewed 8 June 2026 8 min read

Australia records the world's highest skin cancer rates — two in three Australians develop at least one non-melanoma skin cancer by age 70. Solar keratoses are premalignant UV lesions; BCC is locally destructive; SCC can metastasise.

Management starts with biopsy to confirm diagnosis, then excision with appropriate margins. Mohs surgery is preferred for high-risk or facial lesions. PBS-listed therapies exist for advanced BCC (vismodegib) and SCC (cemiplimab) under specialist initiation.

Daily SPF 50+ sunscreen, UPF clothing, and avoiding peak UV hours are the prevention pillars. After a first skin cancer, 50% develop another within five years — surveillance is essential.

Two in three Australians will develop at least one non-melanoma skin cancer (NMSC) by age 70. Australia records more than one million NMSC treatments per year, accounting for the single most expensive cancer to the health system — exceeding even melanoma in total treatment cost due to sheer volume. Around 1,000 Australians die from squamous cell carcinoma each year, predominantly in elderly, immunosuppressed, and rural populations where surveillance and access to treatment are delayed.

The clinical spectrum runs from solar (actinic) keratoses — UV-driven premalignant lesions — through basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), with field cancerisation describing the broader zone of UV damage that generates them. Managing this spectrum is a core general practice skill — from recognising and treating solar keratoses through to knowing when to biopsy, when to excise, and when to refer urgently.

Cancer Council Australia’s Clinical Practice Guidelines for Keratinocyte Cancer, the Australasian College of Dermatologists, and eTG: Dermatology are the primary AU clinical standards.

A. Core clinical — the AU general-practice framework

History

A structured sun-exposure and skin history is the foundation:

Cumulative UV exposure — occupational (outdoor worker, farmer, tradesperson, sports coach), recreational (water sports, gardening, sport), and childhood sunburn history including blistering burns
Skin type — Fitzpatrick I (always burns, never tans) and II (usually burns) carry the highest risk; Fitzpatrick V and VI have lower NMSC risk but are not immune
Prior skin cancers — history of any NMSC dramatically increases the five-year risk of another; approximately 50% develop a subsequent NMSC within five years of their first
Immunosuppression — transplant recipient, biologic therapy (anti-TNF, anti-CD20), long-term oral corticosteroids, haematological malignancy, HIV
Medications — voriconazole (substantially elevated SCC risk in transplant patients), azathioprine combined with UV, hydrochlorothiazide (observational signal for photosensitivity-associated SCC)
Current concern — bleeding, growth rate, non-healing, pain, paraesthesia near the lesion (perineural invasion in SCC)

Examination

Full-body skin examination with good lighting and dermoscopy improves diagnostic accuracy significantly:

Solar keratosis — rough, scaly, reddish-pink papule on sun-damaged skin; sandpaper texture; strawberry dermoscopy pattern
BCC nodular — pearly papule, rolled border, surface telangiectasia, central ulceration; arborising vessels, blue-grey ovoid nests on dermoscopy
BCC superficial — flat pink-red plaque, thread-like border; trunk predominance
BCC morphoeic/infiltrative — scar-like, ill-defined, indurated; high-risk; H-zone of face; may be subtle
SCC invasive — keratotic nodule, ulcerated plaque; dotted vessels, white circles on dermoscopy
SCC in situ (Bowen’s disease) — well-defined erythematous scaly plaque
Keratoacanthoma — rapidly growing dome with central keratin-filled crater; treat as SCC
Lymphadenopathy — assess regional nodes in confirmed or suspected SCC

Investigations

Biopsy is the diagnostic cornerstone. Do not treat a lesion presumed to be a solar keratosis with cryotherapy if clinical features suggest SCC or BCC — biopsy first to confirm:

Shave biopsy for nodular lesions where melanoma differential is not the priority
Punch biopsy for infiltrative or flat lesions and for melanoma-differential pigmented lesions
Excisional biopsy when melanoma cannot be excluded clinically

High-risk SCC staging: lymph node ultrasound for palpable nodes; CT chest/abdomen/pelvis for locally advanced disease; MRI for perineural or orbital extension; PET-CT for advanced staging.

B. Treatment — solar keratoses, BCC, and SCC

Solar keratoses

Cancer Council Australia guidelines endorse multiple effective treatments for solar keratoses:

Cryotherapy (liquid nitrogen) — most common; one to two freeze-thaw cycles; effective for individual lesions; pigmentary change risk in skin of colour
Topical 5-fluorouracil 5% (Efudix) — twice daily for two to four weeks; field treatment; significant expected inflammation is a sign of efficacy, not a complication
Imiquimod 5% (Aldara) or 3.75% (Zyclara) — variable regimens; immune-mediated inflammatory response; effective for field treatment
Diclofenac 3% gel (Solaraze) — twice daily for two to three months; modest efficacy; better tolerated than 5-FU or imiquimod; suitable for sensitive areas
Photodynamic therapy (PDT) — specialist; topical methyl aminolevulinate plus light activation; excellent cosmesis; suitable for field cancerisation on face and scalp
Ingenol mebutate (Picato) — WITHDRAWN by TGA in 2020 following a long-term skin cancer safety signal; do not prescribe

Nicotinamide 500 mg twice daily reduces new NMSC by approximately 23% in high-risk patients (those with two or more prior NMSCs in five years), as demonstrated in the ONTRAC trial (Chen AC et al, NEJM 2015). It is not PBS-subsidised but is inexpensive OTC.

BCC management

For most BCCs, surgical excision with margin is the gold standard per Cancer Council Australia guidelines:

Low-risk nodular/superficial BCC: excision with 3–5 mm margin; high cure rates
High-risk facial, morphoeic, recurrent, or large BCC: Mohs micrographic surgery — tissue-sparing, layer-by-layer margin control, up to 99% cure; specialist dermatologist or Mohs surgeon
Curettage and electrodessication: low-risk superficial BCC on the body
Radiotherapy: for elderly patients or inoperable lesions
Topical imiquimod or 5-FU: suitable for low-risk superficial BCC only — not nodular or infiltrative
Vismodegib (Erivedge) — Hedgehog pathway inhibitor; PBS Authority Required for locally advanced or metastatic BCC; specialist initiation; significant side-effect profile (muscle cramps, alopecia, taste disturbance); Category D in pregnancy

SCC management

SCC carries metastatic potential — the distinction between low-risk and high-risk features directs management urgency:

High-risk SCC features (any one is sufficient): diameter ≥2 cm; depth ≥6 mm; perineural invasion (numbness, paraesthesia); poorly differentiated histology; anatomical site (lip, ear, scalp, temple); immunosuppressed host; recurrent lesion.

Low-risk SCC: excision with 4–6 mm margin
High-risk SCC: excision with 6–10 mm margin or Mohs micrographic surgery; sentinel lymph node biopsy in selected cases; adjunctive radiotherapy for positive margins, perineural invasion, or nodal disease
Advanced/metastatic SCC: cemiplimab (Libtayo) — PD-1 checkpoint inhibitor; PBS Authority Required for cutaneous SCC advanced disease; transformative in what was previously a treatment-poor setting

C. Prevention and surveillance

Sunscreen — daily SPF 50+ broad-spectrum application on exposed skin is the highest-evidence individual preventive intervention. The Nambour SCC trial demonstrated that daily sunscreen application reduced SCC incidence versus discretionary use. Reapply every two hours or after swimming or sweating. Cancer Council SunSmart provides the UV-index-based SunSmart app.

Sun-protective clothing — UPF-rated clothing, wide-brim hat (minimum 7.5 cm brim), and UV400-rated sunglasses.

Avoid peak UV — UV index ≥3, typically 10 am to 3 pm during AU summer; check the SunSmart UV app.

Commercial solariums (sunbeds) — banned in Australia since 2014. Report illegal commercial solarium operations to the relevant state Department of Health.

Post-NMSC surveillance schedule:

Three to six monthly for the first year post-excision
Six to twelve monthly long-term, lifelong for high-risk patients
Three-monthly for immunosuppressed patients
Annual full-body skin examination for all patients with prior NMSC history

Self-examination — teach patients to check their own skin monthly and present promptly for any new, changing, bleeding, or non-healing lesion.

D. Australian operations

MBS billing. Standard consultation items 23, 36, and 44. Skin lesion biopsy/excision items under 30071, 30072, 31230 range based on lesion size and site — histopathology is mandatory and its cost is rebatable. Cryotherapy under item 30192 range. PDT and Mohs micrographic surgery under specialist items. GPCCMP (items 965/967) for chronic NMSC with field cancerisation, multiple cancers, or immunosuppression — allied health coordination including lifestyle counselling and skin cancer education. ATSI Health Assessment (item 715); 75+ Health Assessment (item 705) for integrated skin cancer screening in the annual assessment.

PBS. Topical 5-fluorouracil 5% (Efudix) — general schedule. Imiquimod 5% (Aldara) — general schedule for solar keratosis and superficial BCC; Authority Required for some indications. Diclofenac 3% gel (Solaraze) — general schedule. Methyl aminolevulinate (Metvix) for PDT — Authority Required. Vismodegib (Erivedge) — Authority Required for locally advanced or metastatic BCC; specialist initiation. Cemiplimab (Libtayo) — Authority Required for advanced or metastatic CSCC; specialist initiation. Acitretin — Authority Required for chemoprevention in transplant patients with multiple SCCs. Nicotinamide — over the counter, not PBS-subsidised. Ingenol mebutate (Picato) is withdrawn — do not prescribe.

Outdoor workers and workers’ compensation. NMSC arising from occupational UV exposure may be eligible for workers’ compensation in New South Wales and Victoria — document occupational UV history, duration, and diagnosis clearly in the medical record.

DVA coverage. Veterans are a high-risk population for NMSC due to outdoor service. DVA covers eligible veterans for skin cancer treatment.

E. Special populations

Transplant recipients. The most high-risk population for SCC — approximately 65 times the background rate. Require dermatology shared care, three-monthly surveillance, prophylactic topical 5-FU, consideration of immunosuppression modification, and systemic acitretin for multiple SCCs. Voriconazole significantly elevates SCC risk in transplant fungal prophylaxis — discuss switching with the transplant team if NMSC develops.

HIV and other immunocompromised patients. Elevated NMSC risk proportional to degree of immunosuppression; intensify surveillance.

Genodermatoses. Xeroderma pigmentosum (XP) — extremely high UV sensitivity, childhood NMSC; specialist care. Gorlin syndrome — multiple BCCs from young adulthood, jaw cysts, cardiac fibromata; genetic counselling and specialist dermatology. Muir-Torre syndrome — sebaceous skin tumours plus visceral cancers; Lynch syndrome overlap.

Anogenital SCC. HPV-driven; higher risk in HIV-positive patients; National Immunisation Program HPV vaccination relevant for prevention. Refer to gynaecology or urology for anogenital lesions.

Pregnancy. Excision and biopsy are generally safe in pregnancy. Topical 5-FU (Category D) should be avoided, particularly in the first trimester. Topical imiquimod has limited data. Vismodegib and cemiplimab are contraindicated in pregnancy.

When to escalate

Refer urgently to dermatology, Mohs surgery, or plastic surgery when:

Suspected or confirmed SCC — especially any high-risk feature (>2 cm, ≥6 mm depth, perineural, lip/ear/scalp, immunosuppressed, recurrent, poorly differentiated)
Morphoeic, infiltrative, or large BCC — Mohs micrographic surgery candidate
Suspected lymph node involvement or staging required
Advanced or metastatic disease requiring systemic immunotherapy or Hedgehog inhibitor
Cosmetically or functionally critical location (eyelid, nose, lip, ear)
Immunosuppressed patient with NMSC — accelerated surveillance required
Diagnostic uncertainty after dermoscopy and biopsy

What this article is and is not

This is general health information drawn from Cancer Council Australia Clinical Practice Guidelines for Keratinocyte Cancer, Australasian College of Dermatologists, eTG Dermatology, AMH, RACGP, NPS MedicineWise, and TGA product information. It is not personal medical advice and does not create a doctor–patient relationship. Decisions about biopsy, excision, referral, and surveillance are made with your own GP and treating specialists.

For consumer-friendly AU resources: Cancer Council SunSmart, HealthDirect — Skin cancer, Better Health Channel — Skin cancer, Australasian College of Dermatologists — Find a dermatologist.

Sources cited

Frequently asked questions

How do I tell a solar keratosis from skin cancer?

Solar keratoses are rough, scaly, reddish-pink papules on chronically sun-damaged skin — they 'feel before they see': the sandpaper texture is often palpable before the lesion is prominent. BCC typically presents as a pearly, flesh-coloured papule with rolled edges, surface telangiectasia, and a tendency to bleed or develop a central ulceration — the classic 'rodent ulcer'. Superficial BCC is a flat pink plaque with a fine thread-like border, often on the trunk. SCC presents as a keratotic nodule, ulcerated plaque, or rapidly growing dome-shaped lesion. Any lesion that does not heal within four weeks, bleeds without trauma, or is growing should be assessed clinically with dermoscopy and biopsied if there is any uncertainty.
What is field cancerisation and why does it matter?

Field cancerisation describes a zone of chronically sun-damaged skin where the entire area contains UV-mutated keratinocytes — not just discrete visible lesions. This means multiple solar keratoses, in situ SCCs, and invasive skin cancers can arise and recur across the same anatomical region. Treating individual lesions in isolation (cryotherapy of each spot) is often insufficient. Field treatments that address the whole zone — topical 5-fluorouracil, imiquimod, diclofenac, or photodynamic therapy — are important adjuncts to managing field cancerisation, alongside strict sun protection and regular surveillance.
Which skin cancers need urgent specialist referral?

Urgently refer for specialist assessment: any suspected SCC (which can metastasise to lymph nodes if high-risk or neglected); high-risk BCC features — morphoeic or infiltrative subtype, recurrent, large, central face or H-zone involvement, ill-defined margins; any lesion with perineural symptoms (numbness, paraesthesia near the lesion); suspected lymph node involvement; lesions in immunosuppressed patients; and any suspected advanced or metastatic disease requiring systemic therapy. Vismodegib (for advanced BCC) and cemiplimab (for advanced SCC) are PBS Authority medicines requiring specialist initiation.
Is nicotinamide useful for skin cancer prevention?

Yes, in selected high-risk patients. The ONTRAC trial published in the New England Journal of Medicine in 2015 demonstrated a 23% reduction in new non-melanoma skin cancers in high-risk patients (two or more non-melanoma skin cancers in the preceding five years) taking nicotinamide 500 mg twice daily. Nicotinamide (vitamin B3, not to be confused with nicotinic acid niacin) is inexpensive and available over the counter. It is not PBS-subsidised but is a low-cost preventive option for high-risk patients, recommended alongside sunscreen and surveillance. Benefit does not persist after cessation.
How are transplant patients managed differently?

Organ transplant recipients are at approximately 65 times the SCC risk of the general population due to immunosuppression, particularly azathioprine combined with UV exposure. BCCs are also substantially more common and more aggressive. Management involves dermatology shared care with aggressive surveillance (three-monthly), use of topical chemoprevention (5-fluorouracil), modification of immunosuppression towards less skin-cancer-promoting agents where clinically possible (switching azathioprine to mycophenolate), and systemic acitretin for patients with multiple SCCs. Patients on voriconazole for fungal prophylaxis are at additional elevated SCC risk — switch to an alternative antifungal if NMSC develops.

Source quality

Sources grouped by evidence tier. AU primary tier first; international where AU is silent or lagging; named-author reconstruction where guidelines have not yet caught up. How tiers work.