Histology shows PSEUDOSTRATIFIED CILIATED COLUMNAR epithelium with a chronic inflammatory infiltrate. What does this represent?

Correct answer: C. Lining of the maxillary sinus

• A. A dentigerous cyst has a thin, non-inflamed lining of two to four cells attached at the cementoenamel junction of an UNERUPTED tooth. This tooth was erupted.
• B. An odontogenic keratocyst has a thin, uniform PARAKERATINISED stratified squamous lining of six to eight cells with a palisaded, hyperchromatic basal layer and a corrugated luminal surface, characteristically in a non-inflamed wall.
• C. CORRECT. Pseudostratified ciliated columnar epithelium is RESPIRATORY epithelium — the Schneiderian membrane. Finding it in tissue retrieved from a maxillary molar socket means the antral floor was breached and sinus lining was removed, confirming an OROANTRAL COMMUNICATION. The chronic inflammatory infiltrate reflects the associated sinusitis or local irritation. Confirm the communication clinically — a gentle nose-blowing test, careful inspection, never vigorous probing — and treat by size: under 2 mm usually closes spontaneously with sinus precautions; 2 to 5 mm needs a figure-of-eight suture with precautions; over 5 mm needs a buccal advancement or palatal rotation flap.
• D. A radicular cyst is lined by NON-KERATINISED STRATIFIED SQUAMOUS epithelium of variable thickness with arcading rete ridges, in a fibrous wall densely infiltrated by chronic inflammatory cells. It is the option the recall paired this with, and the EPITHELIAL TYPE is the entire discriminator — squamous versus respiratory.

Note: One genuine nuance: a radicular cyst lying directly against the antral floor can occasionally show RESPIRATORY METAPLASIA in part of its lining. But the straightforward reading of respiratory epithelium in tissue from a maxillary molar socket is sinus lining. Sinus precautions to give: no nose blowing, sneeze with the mouth open, no straws, no smoking, and no forceful spitting for two weeks.