Clinical History
The patient was presented with a long-standing right nasal obstruction, and was examined using plain radiography, which showed a right maxillary sinus opacity.
Imaging Findings
The patient was presented with a long-standing right nasal obstruction, and was examined using plain radiography, which showed a right maxillary sinus opacity.
A CT scan was performed which showed a solitary antrochoanal polyp originating in the maxillary sinus mucosa and emerging through an accessory ostium, filling up the nasal fossa, and finding its
way along to the choana then to the nasopharynx, without bone destruction.
Discussion
The antrochoanal polyp or Killian polyp is an infrequent, benign lesion of maxillary origin (90%); it can also develop from the sphenoidal sinus, the ethmoid sinus, the septum, the palate or the
frontal sinus. The occurrence of choanal polyps is equally frequent in both males and females and these are most prevalent in teenagers and in young adults. Although its pathogenesis has not yet been
elucidated, Killian polyps have typically been described as solitary lesions with little or no association with the allergic state. The relatively low number of submucous glands suggests that the
antrochoanal polyp results from distention of glandular structures. According to Berg, Killian polyp is an intranasal expansion of a mural sinus cyst. Unilateral nasal obstruction is the predominant
symptom. It is often associated with mucopurulent rhinorrhea, and sometimes with headaches and hyposmia. The point of attachment in most cases is the lateral wall of the maxillary sinus. The polyp
emerges through the natural or accessory ostia and, as it elongates, finds its way along to the choana, then to the nasopharynx. Macroscopically, it usually presents as a firm, smooth, translucent
mass, occupying the nasal fossa, whereas the antral part of the polyp is cystic, often containing with a straw-colored fluid. Microscopically, the surface epithelium is generally cylindrical, and the
stroma appears myxoid or fibrous and contains a few mononucleated, inflammatory cells; the number of glands is small. CT scans of the sinuses in coronal and axial sections show a maxillary sinus
opacity with an extension varying in length within the nasal fossa and choana. The walls are distended or thinned, but never eroded; the opacity inside the nasal fossa and cavum is always
significant. An enlargement of the maxillary ostium can occasionally be observed. On MRI, it was found that the antrochoanal polyp has a liquid component, but this examination need only be performed
in cases of suspected malignancy. In general, diagnosis is made on the basis of clinical, CT and pathological data. The two general differential diagnoses are inverted papilloma, a tumor that may
contain calcifications and cause destruction of surrounding bone, and fungus infection; in this last condition, the maxillary sinus wall may appear thickened and the sinus may contain hyperdense
material (tooth filling material), or faint intraluminal calcifications. Treatment is exclusively surgical with cauterization of the pedicle in order to reduce the chances of recurrence.
Differential Diagnosis List