Keratoacanthoma
1. Background information
a. Definition
A rapidly growing, dome-shaped skin lesion with a central keratin plug, originating from hair follicles and clinically resembling squamous cell carcinoma (SCC).
b. Clinical classification
- Solitary keratoacanthoma (most common)
- Multiple keratoacanthomas (rare; syndromic e.g. Ferguson-Smith type)
c. Etiopathophysiology
- Exact cause unclear
Risk factors
- UV exposure (sunlight)
- Increasing age (elderly)
- Immunosuppression
- Trauma
Pathophysiology (AKT concept)
- Rapid keratinocyte proliferation →
- Growth phase (weeks)
- Plateau
- Possible spontaneous regression
AKT key point
- Often considered a variant of well-differentiated SCC → managed as malignant until proven otherwise
d. Differential diagnosis (AKT high-yield)
- Squamous cell carcinoma (most important)
- Basal cell carcinoma
- Actinic keratosis
- Viral wart
- Molluscum contagiosum
2. Assessment
a. Clinical presentation
Classic features (AKT MUST KNOW)
- Rapid growth (weeks)
- Dome-shaped nodule
- Central keratin-filled crater
- Firm, flesh-coloured or erythematous
Common sites
- Sun-exposed areas:
- Face
- Forearms
- Hands
AKT diagnostic clues
- Elderly patient
- History of sun exposure
- Rapid enlargement → key differentiator
Red flags (→ treat as SCC)
- Irregular borders
- Ulceration
- Persistent growth
- Bleeding
b. Relevant investigations
NICE CKS approach
- Urgent specialist assessment required
Definitive diagnosis
- Excision biopsy / histology
AKT pearl
- Cannot reliably distinguish from SCC clinically → always biopsy
3. Management (UK NICE CKS-based)
a. Emergency care
- Not typically required
b. Referral
Urgent referral (2WW skin cancer pathway)
- Any suspected keratoacanthoma
→ due to inability to exclude SCC
c. Primary care management
1. Initial GP role (AKT key)
- Recognise suspicious lesion
- Do NOT reassure or delay
- Arrange urgent 2-week wait referral
2. Specialist management
- Complete surgical excision (standard)
- Curettage ± cautery (selected cases)
3. Other options (specialist-led)
- Intralesional therapies (e.g. methotrexate)
- Cryotherapy (rarely)
4. Follow-up
- Monitor for recurrence
- Skin cancer surveillance
AKT Exam Pearls
- Rapidly growing lesion + central keratin plug = keratoacanthoma
- Cannot distinguish from SCC clinically → treat as SCC
- Always 2WW referral
- Sun-exposed areas in elderly patients
- Histology required for diagnosis
