A 25-year-old has a white wipeable lesion at teeth 12–14 region. It didn't resolve with nystatin and involved deeper layers. The MOST appropriate next step is:

Correct answer: C. Incisional biopsy

• A. Excisional biopsy removes the entire lesion and is used for small (<1cm) lesions likely to be benign — not appropriate for a large suspicious lesion spanning multiple teeth.
• B. Brush biopsy (OralCDx) is a transepithelial sampling tool — it does not adequately sample when deeper tissue involvement is suspected.
• C. Correct. The lesion is: (1) wipeable initially but didn't resolve with antifungal = not simple candidiasis, (2) affects deeper layers = concern for dysplasia or malignancy, (3) large (involving 12–14 region) = >1cm. For a large lesion with failed antifungal treatment and depth involvement, INCISIONAL biopsy (representative sample) is indicated for histopathological diagnosis.
• D. Exfoliative cytology scrapes surface cells — it cannot evaluate deeper layers and is not appropriate when depth involvement is suspected.