Origin of the choanal polyp.

To study the origin of the choanal polyp, the maxillary sinus was surgically explored using a preservative technique. An antral cyst or a cystic rudiment, usually attached to the inferolateral aspect of the sinus wall, was disclosed in 15 patients with this condition. As a part of the choanal polyp, the antral cyst exhibited a macroarchitecture and microarchitecture identical to the structure of the common intramural cyst of the maxillary sinus as studied in nine patients. It is concluded that the choanal polyp develops from the expanding intramural cyst protruding through the maxillary ostium and into the nasal cavity.