Keratoacanthoma

Diagnosis: Keratoacanthoma

Erythematous, dome-shaped, tumor with a central, horn-filled, crater-like depression.

Clinical Presentation

Erythematous, dome-shaped, tumor with a central, horn-filled, crater-like depression.

Clinical History

Submitted by Alaa Saad. Originally posted September 15, 2010.

Treatment

See case discussion.

Differential Diagnosis

• Squamous cell carcinoma (well-differentiated) • Basal cell carcinoma (nodular) • Molluscum contagiosum (giant) • Prurigo nodularis • Verruca vulgaris • Merkel cell carcinoma

Key Learnings

• Rapidly growing, dome-shaped nodule with a central keratinous plug — "crateriform" • Classic evolution: rapid growth over weeks → mature stable phase → spontaneous involution over months • Controversial: many consider KA a well-differentiated SCC variant rather than a truly benign entity • Cannot reliably distinguish from SCC on biopsy — excision is standard of care • Shave biopsy is insufficient — need deep biopsy or excision to see the overall architecture • Multiple KAs: consider Muir-Torre syndrome (mismatch repair deficiency) or Ferguson-Smith syndrome

Tags: keratoacanthoma, alaa saad