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Regression Dermoscopy — SCE Dermatology MCQ

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HardSkin CancerRegression DermoscopySCE Dermatology

An immunosuppressed patient has several slowly enlarging annular plaques with an atrophic centre and a narrow keratotic peripheral ridge. Dermoscopy suggests porokeratosis, but histological confirmation is required. Which biopsy strategy has the highest diagnostic yield?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: A — Sample across the raised peripheral ridge to capture a cornoid lamella

Explanation lettering: B = shown as A · D = shown as B · A = shown as C · E = shown as D · C = shown as E

B is correct. The diagnostic cornoid lamella is a column of parakeratosis over focal dyskeratosis and attenuation of the granular layer at the clinically visible keratotic ridge. A sample confined to the atrophic centre can miss it. Adjacent normal skin does not establish the diagnosis, central scale examination may address a fungal differential but does not demonstrate porokeratosis, and curetting the centre sacrifices the critical rim. Because immunosuppression and changing or thickened areas increase concern for malignant transformation, a separate representative biopsy of any suspicious focus may also be required.

Reference: DermNet porokeratosis: https://dermnetnz.org/topics/porokeratosis