Keratoacanthoma

Definition/diagnostic criteria Keratoacanthoma (KA) is a rapidly growing, dome-shaped tumour with a central keratin-filled crater, commonly resembling a squamous cell carcinoma (SCC). While the diagnosis can be suspected clinically based on the lesion’s distinctive appearance, histological examination is essential to differentiate KA from SCC and other skin neoplasms.

Epidemiology KA is relatively common in the UK, particularly among the elderly population. It predominantly affects individuals over the age of 60, with a slight male predominance. Exposure to sunlight is a significant risk factor, suggesting a correlation with outdoor activities and occupations.

Diagnosis
Clinical features: Keratoacanthomas typically present as rapidly enlarging, round, skin-coloured or erythematous nodules, often on sun-exposed areas such as the face, forearms, and hands. A characteristic feature is the central keratotic plug.

Despite their aggressive initial growth, they may spontaneously regress over a few months. However, distinguishing KA from SCC based solely on clinical presentation is very difficult.

Investigations: The definitive diagnosis is made through histopathological examination, which shows a well-differentiated squamous cell proliferation with a central keratin-filled crater. If a KA is suspected, urgent referral to a dermatologist for biopsy or excision is recommended.

Treatment Treatment of KA involves surgical and non-surgical approaches.

• Complete surgical excision is the most definitive treatment and allows for histopathological examination to confirm the diagnosis and rule out SCC.
• Other treatment options include intralesional methotrexate or 5-fluorouracil, cryotherapy, and curettage with cautery.

Prognosis The prognosis for keratoacanthoma is generally good. Most lesions undergo spontaneous resolution over months, but they can leave scarring – though those presenting for medical attention will usually be excised. Recurrence after treatment is uncommon but can occur, particularly in larger lesions or those on the lower legs.