Hyperplasia
Keratoacanthoma
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Keratoacanthoma
Epidemiology
Onset later in life
More common in men
Pathophysiology
Squamoproliferative, benign epithelial lesions
No longer thought to be associated with malignancy
Not a squamous cell cancer variant
May be difficult to distinguish from SCC (see below)
Risk Factors
Ultraviolet light exposure
Human Papillomavirus
Coal tar derivative exposure
Cigarette
smoking
Chemical carcinogens
Signs
Characteristics
First
Red to skin-colored firm, round
Papule
Rapid growth into dome-shaped
Nodule
May reach up to 1-2 cm in size within weeks to months
Central umbilicated keratinous core
Smooth surface
Later (after 4-6 months)
Lesion regresses over months
Keratin core expelled
Hypopigmented scar remains
Distribution (sun-exposed areas)
Face
Extremities
Differential Diagnosis
Squamous Cell Skin Cancer
Similar grossly and histologically to Keratoacanthoma
Labs
Biopsy
Biopsy lesions suspicious for
Squamous Cell Skin Cancer
(especially larger lesions)
Exam and pathology findings can not always reliably distinguish keratocanthoma from SCC
Complete excision with 3-5 mm margins is preferred overall
Punch Biopsy
is preferred over
Shave Biopsy
(depth may be inadequate otherwise)
Management
Small Keratoacanthoma
Electrodessication and Curettage
Blunt Dissection
Larger Keratoacanthoma
Excision with 3-5 mm margins
Moh's Surgery for difficult areas (esp. in regions with cosmetic concerns)
Other options (non-surgical candidates, multiple lesions, inoperable skin sites)
Topical agents
5-Fluorouracil
5% cream
Apply during rapid growth tid
Use under tape
Occlusion
Effective in 1-6 weeks
Podophyllum 25% in benzoin
Remove central crust and apply every 2 weeks prn
Apply in clinic only due to high concentration
Intralesional injections during rapid growth phase
5-Fluorouracil
intralesional injection
Methotrexate
intralesional injection
5-
Interferon alfa
-2a injection
Oral agents (for multiple lesions)
Isotretinoin
(
Accutane
)
Radiotherapy
Indicated for difficult cosmetic areas
References
Habif (1996) Dermatology, Mosby-Year, p. 638
Higgins (2015) Am Fam Physician 92(7): 601-7 [PubMed]
Luba (2003) Am Fam Physician 67(4):729-37 [PubMed]
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