Antrochoanal polyp


An antrochoanal polyp (ACP) is a solitary polyp that arises within the maxillary sinus but passes through and enlarges the sinus ostium or more commonly an accessory ostium.

The nasal cavity is therefore extended posteriorly into the nasopharynx through the posterior chonae.

The MRI signal characteristics of this case are typical:

T1 - intermediate to low signal

  • T2
    • high homogeneous T2 signal
    • signal may vary if they are chronic and/or if fungal infection is present
  • T1 C+ (Gd) - peripheral enhancement is seen on post-contrast images.