Keratoacanthoma

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Keratoacanthoma
Diagnosis in short

Keratoacanthoma. H&E stain.

LM keratin plug, downward cupping of the epidermis, minimal keratinocyte atypia, +/- keratinocytes with glassy pink cytoplasm
LM DDx squamous cell carcinoma, verruca vulgaris, pseudoepitheliomatous hyperplasia
Signs rapid growth
Prevalence uncommon
Prognosis good
Clin. DDx squamous cell carcinoma

Keratoacanthoma is clinically worrisome lesion that classically arise on the nose. It is abbreviated KA.

General

Clinical

  • May grow rapidly (weeks or months) then involute.
  • Main DDx is squamous cell carcinoma.
  • Exophytic lesion, well-circumscribed.

Gross

  • Raised dome-like lesions with a central crater-like defect.

Microscopic

Features:[2]

  • Expansion of stratum spinosum - pushing tongue-like downward growth of epidermis into the dermis.
  • Keratin collection ("keratin plug") at the center of lesion-superficial aspect.
  • Cells have glassy pink cytoplasm.
  • Minimal/no nuclear atypia.

Note:

  • Classically described as a "volcano lesion" with pale pink cells.
  • May have features of regression - PMNs, fibrosis (???).

DDx:[3]

Image

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LESION, LEFT SIDE OF NOSE, EXCISION:
- KERATOACANTHOMA.
- SOLAR ELASTOSIS.

Micro

The sections show hair-bearing skin with a dome-shaped lesion that consists of a cup-shaped epidermal rim, and a large plug of keratin. The lesion is surrounded by a mild patchy lymphoplasmacytic infiltrate. No mitotic activity is apparent. The keratinocytes have minimal atypia and mature to the surface. A granular layer is present. The lesion is completely excised in the plane of section.

There is no hypergrlanulosis. No koilocytes are seen. Solar elastosis is present.

See also

References

  1. Mandrell JC, Santa Cruz D (August 2009). "Keratoacanthoma: hyperplasia, benign neoplasm, or a type of squamous cell carcinoma?". Semin Diagn Pathol 26 (3): 150–63. PMID 20043514.
  2. Klatt, Edward C. (2006). Robbins and Cotran Atlas of Pathology (1st ed.). Saunders. pp. 378. ISBN 978-1416002741.
  3. Busam, Klaus J. (2009). Dermatopathology: A Volume in the Foundations in Diagnostic Pathology Series (1st ed.). Saunders. pp. 379. ISBN 978-0443066542.