Keratinising skin lesion — RACGP Fellowship MCQ

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HardDermatologyKeratinising skin lesionRACGP Fellowship

A 71-year-old farmer has a tender rapidly growing crateriform nodule on the dorsal hand over six weeks. It is 18 mm with a keratin plug. There is extensive sun damage. What is the most appropriate management?

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Correct answer: C — Urgent excision or biopsy to exclude squamous cell carcinoma

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

The correct answer is E: urgent excision or biopsy to exclude SCC. Cancer Council Australia recommends early excision of the entire lesion given the clinical difficulty of distinguishing keratoacanthoma from well-differentiated SCC—both may present with rapid growth, a crateriform shape, and central keratin plug. The primary concern is that SCC cannot be excluded without histopathological assessment of the entire lesion; partial biopsies may miss diagnostic features. In this case, tenderness and rapid growth are additional red flags for malignancy. Observation (A) risks progression of SCC and unnecessary scarring. Topical antifungal (B) misidentifies the lesion. Cryotherapy (C) destroys tissue needed for diagnosis and is inappropriate without confirmation. Reassurance that keratin plugs are benign (D) is false; a keratin plug is not protective against malignancy.

Reference: Cancer Council Australia Clinical Practice Guidelines for Keratinocyte Cancer, cited in RACGP AJGP article 'Keratin and controversy: A common cutaneous tumour that...' and RACGP Skin Biopsies guide (AJGP Vol. 47, No. 4, April 2018). https://www1.racgp.org.au/getattachment/897d1a8a-d956-49f0-9a1c-b44aba93ad5b/Keratin-and-controversy.aspx