Keratoacanthoma Workup

Updated: Feb 24, 2020
  • Author: Tsu-Yi Chuang, MD, MPH, FAAD; Chief Editor: William D James, MD  more...
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One component of establishing the diagnosis of keratoacanthoma (KA) is tissue examination for histopathology. Shave biopsy results from a keratoacanthoma are indistinguishable from invasive squamous cell carcinoma (SCC); therefore, excisional or deep incisional biopsy of the lesion is preferred.


Histologic Findings

Keratoacanthomas (KAs) are composed of singularly well-differentiated squamous epithelium that show only a mild degree of pleomorphism and likely form masses of keratin that constitute the central core of keratoacanthoma.

Pseudocarcinomatous infiltration in keratoacanthoma typically presents a smooth, regular, well-demarcated front that does not extend beyond the level of the sweat glands.

The term SCC-KA type has been introduced for otherwise classic keratoacanthomas that reveal a peripheral zone formed by squamous cells with atypical mitotic figures, hyperchromatic nuclei, and loss of polarity to some degree. These marginal cells also may penetrate into surrounding tissue in a more aggressive pattern.