FFinalistSouthampton · 2027
Dermatology
AKT · Dermatology/Malignant & pre-malignantlow yield

Keratoacanthoma

Rapidly growing keratinocyte tumour (well-differentiated SCC variant)

Overview

A rapidly growing, dome-shaped nodule with a central keratin-filled crater that classically arises over weeks and may then spontaneously regress. Because it is histologically and clinically hard to separate from well-differentiated SCC, it is generally treated as an SCC — excised, not watched.

Recognise

  • Rapid growth over 4–8 weeks into a firm, dome-shaped, skin-coloured nodule with a central keratin plug/crater ("volcano")
  • Sun-exposed sites in older adults; may involute over months leaving a scar
  • The rapid evolution is the clue — but it cannot reliably be told from SCC without histology

Red flags

  • Indistinguishable from well-differentiated SCC — do not simply observe; excise for histology

Differentials & how to tell them apart

Squamous cell carcinomathe crucial mimic — KA cannot be reliably distinguished clinically, so it is excised and treated as SCC
Nodular BCCpearly, slow-growing, telangiectasia — not the weeks-fast keratin crater
Viral wart / cutaneous hornbenign keratotic lesions — but rapid growth mandates biopsy

Clinical image

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Keratoacanthoma — clinical imagesDermNet

Investigations

Excision biopsy for histology (the whole architecture is needed; the diagnosis is often "cannot exclude SCC").

Management

Surgical excision (treated as a well-differentiated SCC)

  1. 1Excise for histology rather than observing.Gate: A keratoacanthoma cannot be reliably distinguished from a well-differentiated SCC clinically — so EXCISE it (treat as SCC) rather than waiting for the hoped-for spontaneous regression
  2. 2Confirm histology; surveillance for other keratinocyte cancers and sun-damage management.
Surgical excision — first-line — definitive and provides histology

Key points

Even though KA can self-resolve, the inability to exclude SCC means excision is standard. The history of rapid growth over weeks is the recognition cue.

Monitor & prognosis

Histology result; skin-cancer surveillance.

Excellent after excision; may scar if left to regress.

Source: BAD/StatPearls; NICE NG12