Keratoacanthoma ICD-10: L85.8

Benign skin tumor / Sun-related lesion

Often searched as: bump on face that grew fast, skin lump with hole in center, fast growing skin nodule, dome shaped bump on face, crater in skin bump, growth on face that appeared quickly, wart like growth on hands or face, sun damage bump skin…

Clinical urgency level

lowmediumhigh

Systems Affected

skin

Severity Levels

mild

Classic keratoacanthoma on a low-risk site (arm, trunk) following typical rapid growth and spontaneous regression cycle — can be monitored with close follow-up.

moderate

Large or persistent keratoacanthoma on the face, nose, or ear not showing signs of regression — surgical removal recommended to prevent disfigurement.

severe

Locally aggressive variant, perineural invasion, or keratoacanthoma centrifugum marginatum (rapidly expanding peripheral type) — requires urgent wide excision and histologic confirmation to rule out SCC.

Red Flags

A bump that grows very rapidly over 4–8 weeks to 1–2cm (distinguishing feature of KA)
Lesion on the face, nose, lip, or ear where local tissue destruction can cause disfigurement
Lesion not regressing after 3–4 months as expected
Ulceration or bleeding within the lesion
Multiple keratoacanthomas appearing simultaneously (possible Ferguson-Smith syndrome or Muir-Torre syndrome)
Lesion in an immunocompromised patient — higher risk of aggressive behavior

Clinical Presentation

Keratoacanthoma — dome-shaped nodule with central keratin-filled crater on the face

Source: Wikimedia Commons (CC BY-SA 3.0 )

Keratoacanthoma image gallery — DermNet NZ

View gallery on DermNet NZ (image gallery reference)

When to See a Doctor

See a dermatologist promptly for any rapidly growing skin nodule — especially one with a central plug or crater on the face, hands, or sun-exposed areas. Because keratoacanthoma looks nearly identical to squamous cell carcinoma clinically and histologically, a professional evaluation and often a biopsy are needed to distinguish them. Don't wait to see if it regresses on a cosmetically sensitive area.

Differential Diagnosis

Squamous cell carcinoma (primary and critical differential — histology needed)
Basal cell carcinoma (nodular variant)
Molluscum contagiosum (smaller, central dimple)
Wart / verruca (rougher surface, slower growth)
Merkel cell carcinoma (rare — aggressive)
Dilated pore of Winer (single large open comedone — no keratin plug dome)

Comorbidities

Chronic UV damage and actinic keratosis
Muir-Torre syndrome (multiple KAs + sebaceous tumors + internal malignancy — genetic)
Ferguson-Smith syndrome (multiple self-healing KAs — rare genetic)
Immunosuppression (organ transplant, HIV — higher risk)
Prior SCC or other non-melanoma skin cancers

Prognosis

Classic keratoacanthoma is considered benign and often regresses spontaneously within 3–6 months, leaving a depressed scar. However, most dermatologists advocate for surgical removal rather than watchful waiting because: (1) clinical distinction from SCC is unreliable, (2) spontaneous regression leaves a scar regardless, and (3) some lesions are locally aggressive. Surgical excision or Mohs surgery achieves complete cure. Recurrence after removal is uncommon. The rare giant or centrifugum variants may require more aggressive treatment.

Detailed Overview

Causes, Symptoms, and When to Take Action Keratoacanthoma is a benign, rapidly growing skin lesion characterized by a dome-shaped nodule with a central keratin-filled crater. Though generally non-cancerous, it may mimic more aggressive skin tumors. How It Looks Texture: Firm, smooth nodule with a central plug of keratin Color: Flesh-colored, pink, or red Shape: Dome-shaped lesion approximately 1–2 cm in diameter Location: Typically appears on sun-exposed, hair-bearing areas such as the face, dorsal hands, arms, and other sun-exposed regions Why Does It Appear? Keratoacanthoma arises from hair follicle structures. Although the exact cause remains uncertain, predisposing factors may include cumulative sun exposure, previous skin injury or trauma, hormonal factors, and genetic predisposition. The lesion follows a characteristic course: rapid growth, a period of stable appearance, and potential spontaneous regression. Should You Be Concerned? While keratoacanthoma is benign, its clinical and histological similarity to squamous cell carcinoma can make diagnosis challenging. Some subtypes may be locally aggressive or persistent. You should consider seeking medical evaluation if the lesion: Continues growing Develops irregularities in shape or color Becomes symptomatic (e.g., ulceration or bleeding) Can You Prevent It? There is no known way to prevent keratoacanthoma. However: Minimizing sun damage (e.g., UV protection) Avoiding unnecessary trauma to skin Monitoring for new or changing lesions may help with early detection. 👉 How Piel AI Can Help Piel AI allows you to monitor nodular skin changes over time through regular imaging. While not diagnostic, it helps you detect changes in size, shape, or stability — and supports discussions with healthcare providers. Summary Keratoacanthoma is a benign, rapidly growing skin nodule with a keratin-filled center. It typically appears on sun-exposed sites and follows a cycle of growth and possible regression. Resembles squamous cell carcinoma, warranting careful monitoring or evaluation. No prevention is known, but UV protection and lesion tracking are useful.

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