Antrochoanal polyp

Case contributed by Dr Ian Bickle

Presentation

Right-sided nasal blockage. Endoscopy was suggestive of an antrochoanal polyp.

Patient Data

Age: 30 years
Gender: Male
CT

A soft tissue mass is seen in the right maxillary sinus extending into the nasopharynx.

Widening of the bony ostium of the maxillary sinus.

The remainder of the paranasal sinuses are unremarkable.

MRI

The right maxillary sinus, right posterior nasal canal and nasopharynx are occupied with a soft tissue mass.

The mass is seen widening the maxillary ostium.

The tissue is T1 isointense and intensely T2 hyperintense with heterogeneous, largely rim enhancement.

Case Discussion

An antrochoanal polyp (ACP) is a solitary polyp that arises within the maxillary sinus but passes to the nasopharynx through the sinus ostium and posterior nasal cavity,

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.

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