A lesion on the tongue, when biopsied, shows keratin-filled crypt and squamous epithelium projections. What is the diagnosis?

Correct answer: D. Pleomorphic adenoma

• A. Granular cell tumor can occur on the tongue but has distinct large cells with granular eosinophilic cytoplasm histologically.
• B. Schwannoma is a nerve sheath tumor with distinctive Antoni A/B patterns, not papillary projections.
• C. Fibroma is a benign connective tissue lesion — it does not involve the tongue's minor salivary glands.
• D. Correct. Pleomorphic adenoma is the exception — it arises from salivary gland tissue and is NOT expected as a differential for tongue surface lesions. The others (fibroma, granular cell tumor, schwannoma) all occur on the tongue. When asked 'which is NOT a differential for tongue lesion,' pleomorphic adenoma is the answer.

Note: The source PDF asked which is the EXCEPT among tongue lesion differentials — pleomorphic adenoma (salivary gland origin) is the answer.