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BMJ Case Rep. 2010; 2010: bcr12.2009.2578.
Published online 2010 April 12. doi:  10.1136/bcr.12.2009.2578
PMCID: PMC3047578
Unusual presentation of more common disease/injury

Nasal mass mimicking antrochoanal polyp

Abstract

Sphenochoanal polyp is a rare form of choanal polyp. As the name suggests, it originates from the sphenoid sinus and extends down the choana and nasopharynx. If wrongly diagnosed as an antrochoanal polyp, it can lead to unnecessary exploration of the maxillary sinus and incomplete removal of the sphenoid component of polyp. Here we report a case of 40-year-old woman who presented with history of progressive left nasal obstruction and mass in the oropharynx. A diagnosis of sphenochoanal polyp was made on the basis of nasal endoscopy and computed tomography scan. The polyp was removed endoscopically. We discuss the clinical presentation, management and review of the literature of this clinically mistaken entity.

Background

Choanal polyps are solitary, benign tumours which come from one of the paranasal sinuses and through the corresponding drainage ostium project themselves to the choana, nasopharynx and sometimes up to oropharynx.1 Both types of choanal polyps produce almost similar symptoms with indistinguishable clinical findings for the unsuspecting clinician. The possibility is therefore to conclude prematurely that a choanal polyp is of antral origin.2

A sphenochoanal polyp is a solitary mass that arises from the sphenoid sinus, exits through the sphenoid ostium, passes across the spenoethamodial recess and reaches into the choana.

Sphenochoanal polyp is rare and often mistaken for its more common counterpart—the antrochoanal polyp.2 Sphenoid sinus disease often has an insidious onset with non-specific symptoms. Furthermore, optimal physical examination is difficult due to the relative inaccessibility of the sinus.3

Nasal endoscopy serves as essential diagnostic tool while computed tomography (CT)/magnetic resonance imaging (MRI) of paranasal sinuses (PNS) is the conclusive investigation for confirming the diagnosis and planning the surgical treatment.3 Polyps from the spenoethamodial recess are often neoplastic; moreover, various pathological findings in the region, including vascular neoplasm, vascular malformations, and encephaloceles, can increase the risk of surgery in this region.4 Therefore a preoperative diagnosis is important as it influences the extent of surgery required.3

This paper serves to highlight the need to be constantly vigilant as sphenochoanal polyp may occasionally spring surprises on the clinician.

Case presentation

We report a case of a 40-year-old woman who presented to the ear, nose and throat (ENT) department of the People’s Hospital, Bhopal with complaints of left nasal obstruction over the preceding year which had progressively become bilateral. She was also complaining of left sided headache, loss of nasal twang, mouth breathing and a lump in her throat for the past 3–4 months. The patient did not have any other ENT complaints. She also had history of allergy to dust and pollens.

On examination there was no external nasal deformity. On anterior rhinoscopy a solitary smooth glistening, pale polypodial mass occluding the whole posterior part of the left nasal cavity was seen. Routine nasal endoscopy with zero degree scope confirmed the diagnosis of the polyp. The inferior, middle, and superior turbinates and respective meati were normal. The polyp was coming down from the sphenoethamoidal recess. No abnormality was detected in the right nasal cavity. The polyp was occluding the whole nasopharynx and upper part of the oropharynx. Bilateral air entry was absent but perception of smell was present. A smooth, pale, spherical mass was seen hanging in the oropharynx. The remainder of the examination was within normal limits.

Investigations

Coronal section of a non-contrast CT scan of the paranasal sinuses demonstrated partial opacification of the sphenoid sinus between the two septa of the sinus (fig 1).The sphenoid mass was contiguous with the intranasal mass and extended posteriorly through the left choana, filling up the nasopharynx and extending downward to the oropharynx (fig 2). The other paranasal sinuses were clear. On the basis of nasal endoscopy and CT scan findings, a probable diagnosis of sphenochoanal polyp was made. Surgical removal of polyp was planned under general anaesthesia.

Figure 1
Coronal section of non-contrast computed tomography scan of paranasal sinuses, demonstrating partial opacification of sphenoid sinus between the two septa of sinus.
Figure 2
The sphenoid mass was contiguous with the intranasal mass and extended posteriorly through the left choana, filling up the nasopharynx and extending downward to the oropharynx.

Differential diagnosis

The differential diagnosis includes antrochoanal polyp, hypertrophied adenoids, Thornwaldt cyst pituitary tumours, lymphoma, and carcinoma.5

Treatment

During the procedure, by tracing the polyp proximally, we were able to confirm its exit through the ostium of the sphenoid sinus on the left side. The sphenoid ostium was enlarged by the stalk. The ostium was further widened medially and inferiorly by Karison’s punch to allow access for the removal of the sphenoid component of the polyp. The polyp was delivered in toto transorally. Grossly the sphenoid component was thin cystic while the pharyngeal component was thick fibrous (fig 3). Histopathology confirmed a benign sinonasal allergic polyp with cyst containing clear fluid.

Figure 3
Grossly the sphenoid component was thin cystic while the pharyngeal component was thick fibrous.

Outcome and follow-up

The patient made a good postoperative recovery. At 3 months follow-up she was symptom-free and there was no evidence of recurrence.

Discussion

A choanal polyp is defined as an isolated solitary sinus mass or cyst which has passed through the sinus ostium and protruded into the boundaries between the nasal cavity and nasopharynx, the choana.2 These polyps can arise from the maxillary sinus, sphenoid and ethmoid, there being questions in relation to its formation from the frontal sinus. According to Dadas, 4–6% of all nasal polyps are the antrochoanal type. Isolated sphenochoanal polyps are extremely rare. Sphenochonal and ethamochoanal polyps are even more uncommon.1 Only one case of simultaneous antrochoanal polyp and sphenochoanal polyp was reported in the literature.3 Sphenochoanal polyps are difficult to document. They can be present in any age group. To the best of our knowledge the youngest patient reported to have a sphenochoanal polyp was a 3.8-year-old female, and was the only case in which the polyp had completely regressed.6

Most sphenochoanal polyps are not associated with other sinus diseases, although in some cases other sinuses are affected, possibly as a result of blockage by the polyp.7 Sphenochoanal polyp may have a variety of anatomical origins. Although most sphenochoanal polyps arise from the sphenoid ostium, some have been reported to originate in adjacent areas and the sinus. In our case it originated from the sphenoid sinus.3

Choanal polyps have a firmer consistency than nasal polyps owing to their extensive fibroblastic activity. They are believed to arise from an expanding intramural cyst that protrudes through the ostium of the sinus into the nasal cavity. The pathogenesis of the cyst may involve thrombosis of lymphatic vessels following sinus inflammation. Preoperative identification of the sinus from which a choanal polyp arises is important because the site of origin of the polyp in the sinus must be resected in order to minimise recurrence. This consideration may influence the surgical approach.7 In our case the sphenoid sinus was divided into three parts by two septa and the polyp arose from the middle part.

For descriptive purpose, clinicians have divided them into inflammatory and non-inflammatory polyps, with greater prevalence of the former.3 Histopathology is of the utmost importance as, unlike antrochoanal polyps, sphenochoanal polyps have higher chances of exhibiting neoplastic pathology, most often inverted papilloma.1

Downward extension of intracranial pathology must also be considered. CT or MRI serve as invaluable tools for making the differential diagnosis in these cases. Because most choanal polyps are not associated with other sinus diseases, a finding of an opaque sphenoid sinus and a clear maxillary sinus is a likely indicator that the polyp is sphenochoanal, even if its origin cannot be clearly identified. If both the sphenoid and maxillary sinuses are opaque, it is important to identify the continuity of the polyp with its origin at surgery. An antrochoanal polyp originates in the middle meatus; in contrast, a sphenochoanal polyp passes between the nasal septum and the middle turbinate, leaving the middle meatus clear.7

Management of choanal polyps involves complete excision of the polyp including its pedicle and its sight of origin within the sinus. Endoscopic sinus surgery offers excellent views of the sinuses and is associated with lower recurrence rates than simple polypectomy.7

Tosun et al8 reported that almost 50% of sphenochoanal polyps reported in the literature occurred in children. So the most aggressive surgical approach should be avoided. Lopatin suggested that the basic concept of functional endoscopic sinus surgery (FESS) of not manipulating the sinus mucosa (as long as the improvement in drainage and aeration to the PNS tends to restore normal sinus mucosa) is not applicable to choanal polyps. According to Lopatin, removal of damaged mucosa from the sinus during polyp removal by FESS is preferable, since it may be the cause of the recurrence.1 Simple avulsion of the polyp with forceps or snare will result in a 25% rate of recurrence. Gradual debulking of the polyp with a microdebrider facilitates the ability to trace the pedicle to the offending sinus and thus serves not only a therapeutic role, but a diagnostic one as well.2 Operative complications of endoscopic sphenoid surgery are rare but the surgeon must be aware of the close proximity of critical anatomical structures surrounding the sphenoid sinus.3

Learning points

  • We attempt to highlight and alert the clinician that, although antrochoanal polyp is the most common type of choanal polyp, the origin of the polyp from another sinus is possible and should be taken into consideration.
  • CT scan is a valuable tool for confirming the diagnosis.
  • While performing sphenoid surgery the surrounding critical structures should be kept in mind.

Acknowledgments

My patient for her co-operation.

Footnotes

Competing interests: None.

Patient consent: Patient/guardian consent was obtained for publication.

REFERENCES

1. de Jesus EPF, Goto EY, Marono SAM, et al. Sphenochoanal polyp – case report and literature review. Int Arch Otorhinolaryngol 2005; 9(4): Oct/Dec (8°)
2. Soh KBK, Tan KK. Sphenochoanal polyps in Singapore: diagnosis and current management. Singapore Med J 2000; 41: 1848–87. [PubMed]
3. Bist SS, Kumar R, Saurabh V, et al. Isolated sphenochoanal polyp: a rare clinical entity. Indian Journal of Otolaryngology Head Neck Surg 2007; 59: 56–7. [PMC free article] [PubMed]
4. Martin TJ, Smith TL, Smith MM, et al. Evaluation and surgical management of isolated sphenoid sinus disease. Arch Otolaryngol Head Neck Surg 128: 1413–9. [PubMed]
5. Ken Y, Ho SY, Yanagisawa E. Endoscopic view of a sphenochoanal polyp. Ear, Nose & Throat Journal 2000; 79: 546–8. [PubMed]
6. Lim WK, Sdralis T. Regression of a sphenochoanal polyp in a child. The Laryngoscope 2004; 114: 903–5. [PubMed]
7. Tysome JR, Saleh HA. Sphenochoanal polyp presenting with concomitant nasal polyps. Int J Pediatr Otorhinolaryngol 2000; 54: 163–6. [PubMed]
8. Tosun F, Yetiser S, Akcam T, et al. Sphanochoanal polyp: endoscopic surgery. Int J Pediatr Otorhinolaryngol 2001; 58: 87–90. [PubMed]

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