Antrochoanal polyps.

The antrochoanal polyp, a benign solitary polypoid lesion, usually arises in a maxillary sinus, opacifying and enlarging the sinus cavity without bone destruction. It passes through the ostium of the sinus into the choana, and from there into the posterior nasopharynx. The soft tissue mass does not erode or destroy contiguous soft tissue or bony structures. In this sequence of events, its radiologic findings are characteristic. Five case reports are presented, and the differential diagnosis is discussed.