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Chapter 104: Keratoacanthoma

Shirley Lin; Kristin Bibee

KERATOACANTHOMA

Therapeutic Approach

Keratoacanthoma (KA) is common skin tumor that arises predominantly on sun-exposed areas. Clinical manifestations of KA include solitary KA and multiple KAs, and can present in a sporadic fashion, inherited fashion, or in association with inflammatory diseases. Provoking factors include immunosuppression/immunodeficiency, electromagnetic radiation, trauma, chemical factors, drugs that influence the cell cycle, and foreign bodies. Solitary KAs are firm crateriform nodules 1 to 2 cm in diameter, with the giant variant greater than 2 to 3 cm. Multiple KAs can present as KA centrifugum marginatum (persistent peripheral growth), Ferguson-Smith type (1-100 s of noncrateriform nodules), Gryzbowski type (100 s to 1000 s of 1 to -5 mm follicular papules and larger crateriform nodules), or Witten-Zak type (1-5 mm follicular papules and larger nodules). In the authors’ experience, surgical therapy is usually initiated with solitary lesions, with injected medications usually reserved for numerous or recalcitrant cases. See Table 104-1.

Table 104-1Keratoacanthoma Treatment Table
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Table 104-1 Keratoacanthoma Treatment Table
MEDICATION NAME INDICATION MECHANISM OF ACTION DOSING ADVERSE EFFECTS SUGGESTED MONITORING LEVEL OF EVIDENCE (REFERENCE)
Topical Therapy
Imiquimod Solitary KA Immunomodulatory 5% cream, apply QOD Skin irritation None IV1-3
5-Fluorouracil Solitary KA, Multiple KA Chemotherapeutic 5% ointment, apply 2-3× daily Skin irritation None IV4-6
Systemic Therapy
Oral retinoids Multiple KA Anti-inflammatory, antiproliferative

Acitretin 0.5-1.0 mg/kg/d

Isotretinoin 1.5 mg/kg/d

 Teratogenic, dry skin, cheilitis, alopecia, dry eyes, rhinitis, increased lipids and liver enzymes. Contraindicated in renal disease, liver disease, pregnancy or breastfeeding.

CBC, CMP, lipid panel, pregnancy test (in the United States) before first dose

CBC, CMP, lipid panel q1mo to q3mo

 IV7-10
Cyclophosphamide Multiple KA Immunosuppressive

IV pulse of 1 g/mo

Oral 100 mg QD

 Hemorrhagic cystitis, amenorrhea, myelosuppression, alopecia, nausea, vomiting

CBC, lipid panel before first dose

IV: check 10 d after starting tx, then every 2-4 wk

Oral: check 7 d after starting tx, then at least once every 3 wk

 IV11-14
Erlotinib Multiple KA EGFR inhibitor 150 mg QD Diarrhea, rash, nausea, fatigue, stomatitis. Caution in patients using other CYP3A4 inhibitors None IV15,16
Intralesional Drugs
Methotrexate Solitary KA, Multiple KA Chemotherapeutic 12.5-25 mg/wk (25 mg/mL) Local pain, erythema, crusting, ulceration, necrosis. Contraindicated in renal disease, liver disease, pregnancy or breastfeeding. CBC, CMP before first dose IB17-24
5-Fluorouracil Solitary KA, multiple KA Chemotherapeutic 25-50 mg/wk (50 mg/mL) Local pain, erythema, crusting, ulceration, necrosis. Contraindicated in liver disease, pregnancy or breastfeeding. CBC before each dose IV22,23,25-28
Interferon alpha Solitary KA, Multiple KA Immunomodulatory, chemotherapeutic, antiproliferative 3 mU TIW (3 mU/mL) Local pain, acute fever, myalgias, flu-like symptoms. Contraindicated in renal disease, liver disease, pregnancy or breastfeeding. CBC, CMP before first dose and at wk 2, 8, and 12 and every 6 mo thereafter IV22,23,29,30
Bleomycin Solitary KA, Multiple KA Antineoplastic, antibacterial 0.2-0.4 mg/wk ...

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