Overview

Keratoacanthoma (KA) is a relatively common, rapidly growing skin tumor that typically appears as a dome-shaped nodule with a central crater filled with keratin (a thick, scaly material). It most often develops on sun-exposed areas of the skin such as the face, forearms, hands, and neck. While keratoacanthoma resembles squamous cell carcinoma (a type of skin cancer), it is generally considered a low-grade, benign tumor that can sometimes regress on its own. However, because of its similarity to skin cancer, keratoacanthoma is often surgically removed for both diagnostic and therapeutic purposes.

Causes

The exact cause of keratoacanthoma is not fully understood, but several factors have been identified that increase the risk of developing this skin lesion:

• Sun exposure: Chronic ultraviolet (UV) radiation from the sun is the most significant risk factor, making KA more common in fair-skinned individuals who spend a lot of time outdoors.
• Age: It primarily affects middle-aged and older adults, usually over the age of 50.
• Skin injury: KA can sometimes develop in areas of previous trauma, burns, or surgical scars.
• Genetic predisposition: People with a family history of skin cancers or specific syndromes like Muir-Torre syndrome are at higher risk.
• Immunosuppression: Individuals with weakened immune systems, such as organ transplant recipients, are more prone to keratoacanthomas.
• Carcinogenic chemicals: Exposure to certain chemicals like tar or industrial compounds may contribute to its development.

Symptoms

Keratoacanthoma presents with distinctive clinical features that make it recognizable in most cases:

• Rapid growth: The lesion typically grows quickly over several weeks, reaching a size of 1-3 centimeters.
• Dome-shaped nodule: A rounded, firm bump with a characteristic central depression or crater filled with keratin.
• Skin coloration: The surrounding skin may appear reddish, with the nodule being skin-colored or slightly pink.
• Painless: Generally, keratoacanthomas are not painful but may cause tenderness if irritated or inflamed.
• Common locations: Most often appears on sun-exposed areas like the face, forearms, hands, ears, and neck.
• Spontaneous regression: Some keratoacanthomas may shrink and resolve on their own over months, leaving behind a scar.

Diagnosis

Diagnosing keratoacanthoma involves clinical evaluation and histopathological confirmation:

• Clinical examination: A dermatologist examines the lesion’s size, shape, and growth history.
• Skin biopsy: A biopsy is usually performed to distinguish keratoacanthoma from squamous cell carcinoma, as the two can appear very similar under the microscope.
• Histopathology: Pathologists analyze tissue samples to identify typical features of KA, such as well-differentiated squamous cells and a central keratin plug.
• Differential diagnosis: The main concern is ruling out skin cancers, particularly squamous cell carcinoma, due to overlapping features.

Treatment

Although keratoacanthomas can regress spontaneously, treatment is often recommended due to diagnostic uncertainty and cosmetic concerns:

• Surgical excision: Complete surgical removal is the most common treatment, providing both diagnosis confirmation and cure.
• Curettage and electrodesiccation: Scraping off the lesion followed by cauterization, typically used for small lesions.
• Cryotherapy: Freezing the lesion with liquid nitrogen, effective for superficial keratoacanthomas.
• Topical treatments: In select cases, topical chemotherapy agents like 5-fluorouracil (5-FU) or imiquimod cream may be used.
• Radiotherapy: Rarely used, but may be considered for patients who cannot undergo surgery.
• Regular follow-up: Monitoring for recurrence or development of new lesions, especially in high-risk patients.

Prognosis

The prognosis for keratoacanthoma is generally excellent:

• Benign nature: KA is typically non-cancerous and rarely spreads to other parts of the body.
• Low recurrence risk: Complete excision usually results in a permanent cure with minimal chance of recurrence.
• Spontaneous resolution: Some lesions may regress without intervention, although scarring can occur.
• Importance of early treatment: Early diagnosis and removal reduce cosmetic damage and help rule out squamous cell carcinoma.
• Favorable outcome: With appropriate treatment, most individuals recover fully with an excellent cosmetic result.

Keratoacanthoma is a generally harmless skin condition that responds well to treatment. Due to its resemblance to skin cancer, professional evaluation is always recommended for proper diagnosis and management.