Keratoacanthoma

Keratoacanthoma (KA) is a benign but often rapidly growing skin tumor that resembles squamous cell carcinoma (SCC). It is typically considered a low-grade, well-differentiated form of SCC. Although it generally has a good prognosis and may resolve on its own, keratoacanthomas can be challenging to distinguish from squamous cell carcinomas, which can be malignant.

Key Features of Keratoacanthoma:

• Appearance:
  • Shape: KA usually appears as a dome-shaped, raised nodule or mass with a central crater filled with keratin (the protein found in skin and nails). This gives it the characteristic 'volcano-like' appearance.
  • Size: It typically ranges from 1 to 3 cm in diameter, although it can sometimes grow larger.
  • Color: The lesion may be flesh-colored, red, or brown. The center may be keratinous (yellowish or white), often forming a scab or crust.
  • Surface: The surface is often smooth or slightly rough and scaly, with a prominent central keratin plug.
• Location:
  • Common Areas: Keratoacanthomas are most commonly found on sun-exposed areas of the skin, such as the face, ears, neck, upper extremities, and scalp.
  • Frequency: They are more common in older adults (especially those over 50 years old) and people with fair skin, due to the cumulative effects of sun exposure.
• Growth Pattern:
  • Rapid Growth: One of the hallmark features of keratoacanthoma is its rapid growth, often reaching its full size within a few weeks to months.
  • Spontaneous Regression: In many cases, KA will regress spontaneously after several months (typically 6–12 months), shrinking and flattening out on its own. However, this can leave behind scars or pigment changes.
• Symptoms:
  • Painless: Keratoacanthomas are typically painless, though they may become itchy or tender as they grow or become ulcerated.
  • Cosmetic Concerns: The appearance of the lesion is often the primary concern, especially if it appears on the face or other visible areas.
• Causes and Risk Factors:
  • UV Exposure: Chronic sun exposure is a significant risk factor for developing KA. The lesion often appears in areas with the most sun exposure over time.
  • Immunosuppression: Individuals who are immunocompromised (e.g., organ transplant recipients, those on immunosuppressive drugs) may be at higher risk for developing KA.
  • Age: KA is more common in older adults, typically those over 50, although it can occur at any age.
  • Genetic Predisposition: While not hereditary, individuals with genetic skin conditions (like xeroderma pigmentosum, a condition that increases skin cancer risk due to UV damage) may be at increased risk.
• Diagnosis:
  • Clinical Examination: KA is often diagnosed based on its characteristic appearance: a dome-shaped nodule with a central keratin-filled crater.
  • Skin Biopsy: A skin biopsy is essential for distinguishing KA from other skin lesions, particularly squamous cell carcinoma (SCC). A biopsy will show:
  • Histological Features:
    • Exophytic growth: The lesion grows outward from the skin.
    • Central keratin plug: A central keratinous mass or plug is commonly present.
    • Mild atypia in cells at the periphery of the tumor.
• Treatment:
  • Surgical Excision: The most common and definitive treatment for keratoacanthoma is surgical excision, especially if the lesion is causing cosmetic concerns or if there's suspicion of malignant transformation. Excision typically results in a low recurrence rate.
  • Curettage and Electrodessication: This technique involves scraping the lesion off and using electrical currents to remove remaining tumor tissue. It's typically reserved for smaller lesions and those that are not located in high-risk areas (e.g., face).
  • Cryotherapy: In some cases, cryotherapy (freezing) may be used to treat KA, especially in lesions that are not large or deep.
  • Topical Treatments: If the lesion is small and superficial, topical treatments like 5-fluorouracil (5-FU) or imiquimod may be used. These treatments are generally not as effective as surgical excision but may be considered for cases where surgery is not preferred.
  • Observation: In cases where the lesion is small, non-invasive, and located in a low-risk area, observation may be an option, especially since KA can often resolve on its own. However, because of its potential to mimic squamous cell carcinoma, biopsy and close monitoring are essential.
• Prognosis:
  • Benign Nature: Keratoacanthomas are generally benign and are not considered life-threatening. However, they can cause significant cosmetic damage or leave scars after resolution.
  • Recurrence: If not fully excised or if the initial diagnosis is uncertain, KA can recur. If the lesion is left untreated, it may grow larger and become ulcerated.
  • Malignant Potential: While keratoacanthomas are typically benign, they can sometimes transform into squamous cell carcinoma (SCC), particularly if not adequately treated. This is why a biopsy and appropriate treatment are important to rule out malignant behavior.
• Prevention:
  • Sun Protection: Since UV radiation is a major risk factor for KA, using sunscreen, wearing protective clothing, and avoiding excessive sun exposure (especially during peak hours) are essential steps in prevention.
  • Skin Surveillance: Regular self-exams and on oncodermatologist check-ups are important for individuals at risk of developing skin tumors like KA, especially those with a history of sun exposure.

Summary:

Keratoacanthoma (KA) is a benign, rapidly growing skin tumor that resembles squamous cell carcinoma. It often regresses spontaneously but can cause significant cosmetic concern or lead to scarring. Treatment typically involves excision or curettage, and the lesion's potential to transform into SCC makes a biopsy critical. Sun protection and regular skin checks are key for preventing and monitoring skin tumors like KA.