Nasal Polyps are most often seen in patients with allergic rhinitis. A nasal polyp forms gradually from localized swelling of the sinus mucosa or from the nasal mucosa.. At first, the polyp is small. With each recurrence of submucosal edema, it becomes larger, until it appears as a smooth, pale tumor. In most instances, polyps are multiple. They can be moved back and forth and can cause obstructive symptoms when they protrude into the airway. They may be large or numerous enough to occlude the nose completely. In some instances, a single polyp arises from the maxillary antrum ostium and grows posteriorly into the choana and even down to the oropharynx. This is called an antro-choanal polyp.