A whitish lesion is noted in the floor of the mouth beneath the tongue. Which lesion belongs in the differential diagnosis?

Correct answer: B. Oral lymphoepithelial cyst

• A. Mandibular tori are bony, hard, normal-coloured lingual protuberances on the lingual plate above the mylohyoid line, not a whitish mucosal lesion.
• B. CORRECT. The ORAL LYMPHOEPITHELIAL CYST is a small, well-circumscribed, yellow-white submucosal nodule arising in lymphoid tissue. The floor of the mouth is one of its characteristic sites, along with the ventral tongue and the tonsillar region. It is benign, and simple excision is curative.
• C. The parotid duct opens on the BUCCAL mucosa opposite the maxillary second molar, not in the floor of the mouth. Submandibular sialoliths do occur here, but they present with mealtime swelling and pain rather than a white lesion.
• D. A ranula is a BLUISH, translucent, fluctuant swelling from a damaged sublingual gland duct — the colour is wrong for a whitish lesion.

Note: The full floor-of-mouth differential: lymphoepithelial cyst, ranula, dermoid cyst (doughy midline swelling), sialolith with obstructive symptoms, and — the one that must never be missed — squamous cell carcinoma. The floor of mouth and lateral tongue are the highest-risk intraoral sites. Any white lesion that does not wipe off and does not resolve in two weeks gets a biopsy.