What are histologic features of keratoacanthoma (KA)?

Updated: Jan 30, 2020
  • Author: Ginard I Henry, MD; Chief Editor: Gregory Gary Caputy, MD, PhD, FICS  more...
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On histologic examination, keratoacanthomas have an overall hemispheric shape with a keratin-filled crater and overhanging edges. Mitotic figures are present, secondary to the accelerated growth. Basaloid cells are found toward the periphery. Eosinophils also may be common. An overall slight mild pleomorphism is detected. In general, the epithelium is well differentiated and has an abundant ground-glass cytoplasm. At the margin, evidence of a pushing edge is present. This is characterized by an inflammatory rim with extension into the muscle. Perineural and vascular invasion also can be observed. Immunohistochemical staining can help differentiate keratoacanthomas from other epidermal carcinomas. Filaggrin is a histidine-rich protein that is found in the horny and granule layers of the dermis. It is ubiquitous in keratoacanthoma but uncommon in carcinoma. [4, 5]

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