Keratoacanthomas are very characteristic-appearing lesions on the skin that also look very distinctive on histopathology. I get these confused on histopathology with molluscum contagiosum, so I think this is an important condition to know.

Gross Appearance

Keratoacanthomas begin as flesh-colored papules, most commonly on the lower eyelid, that rapidly develops into a dome-shaped nodule with a central keratin-filled crater with elevated and rolled margins.
Over the next 3-6 months, there is typically gradual involution.

Histopathology

The histopathologic description for keratoacanthomas is acanthosis (increased thickness of all layers of epithelium except for keratin layer) with hyperkeratosis (increased thickness of keratin layer) and a central keratin crater, often with atypia and mitoses.
Stromal invasion should be considered a well-differentiated squamous cell carcinoma.

Key Facts

Keratoacanthomas are considered well-differentiated keratinizing squamous cell carcinomas.
They tend to present in middle-aged and elderly patients.
There is an increased incidence of keratoacanthomas in patients who are immunocompromised.

Management

An incisional biopsy can be performed initially to confirm the diagnosis before total excision, or an excisional biopsy can be performed.

References and Additional Reading

Basic and Clinical Science Course, Section 4: Ophthalmic Pathology and Intraocular Tumors. American Academy of Ophthalmology, 2017-2018 edition.
Basic and Clinical Science Course, Section 7: Orbit, Eyelids, and Lacrimal System. American Academy of Ophthalmology, 2017-2018 edition.

Do you have any suggestions on what else might be important to remember about keratoacanthomas that may show up on the OKAP? Do you have any tips for helping to remember all of this information? Do you have any requests for specific topics to cover? Leave a comment or contact us!