Keratoacanthoma

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

General

Generally considered to be benign.
- Rare reports of metastases suggesting it may be a form of squamous cell carcinoma.^[1]

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.

Keratoacanthoma. (WC)

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]

Verruca vulgaris.
Conventional squamous cell carcinoma of the skin with a cup-shape.
Pseudoepitheliomatous hyperplasia.

Image

Keratoacanthoma. (WC)
Keratoacanthoma. (WC/euthman)
Keratoacanthoma. (WC/euthman)
Keratoacanthoma. (WC/euthman)

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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.

References

↑ 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.
↑ Klatt, Edward C. (2006). Robbins and Cotran Atlas of Pathology (1st ed.). Saunders. pp. 378. ISBN 978-1416002741.
↑ Busam, Klaus J. (2009). Dermatopathology: A Volume in the Foundations in Diagnostic Pathology Series (1st ed.). Saunders. pp. 379. ISBN 978-0443066542.

[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.

[Ref_Klatt378-2] Klatt, Edward C. (2006). Robbins and Cotran Atlas of Pathology (1st ed.). Saunders. pp. 378. ISBN 978-1416002741.

[Ref_Derm379-3] Busam, Klaus J. (2009). Dermatopathology: A Volume in the Foundations in Diagnostic Pathology Series (1st ed.). Saunders. pp. 379. ISBN 978-0443066542.

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Keratoacanthoma

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