A photograph shows a very small, white lesion on the soft palate that cannot be wiped off. All of the following are reasonable differential diagnoses EXCEPT:

Correct answer: B. Pleomorphic adenoma

• A. Early squamous cell carcinoma can certainly present as a white non-wipeable patch and must remain in the differential for any persistent leukoplakia.
• B. Correct — this is the EXCEPTION. PLEOMORPHIC ADENOMA is a benign SALIVARY GLAND TUMOUR presenting as a firm, painless, SUBMUCOSAL SWELLING covered by normal-coloured mucosa. Although the posterior lateral hard palate is its commonest intra-oral site, it is a mass lesion, not a white surface plaque. A flat white patch is a surface epithelial change; a pleomorphic adenoma is a deep mass.
• C. Hyperkeratosis is a common cause of a non-wipeable white patch anywhere in the mouth.
• D. Nicotine stomatitis produces a diffuse white palatal keratosis with red inflamed minor salivary duct openings — a legitimate differential for a white palatal lesion.