Sinonasal angiomatous polyp

A 48-year-old man presented with bilateral nasal blockage, anosmia, headache, rhinorrhoea, and bilateral hearing loss. The symptoms were present for more than 3 years. These became progressively worse, even after trying several sprays, antihistamines, and a course of oral steroids. Anterior rhinoscopy showed bilateral nostrils filled with polyps and greenish secretions. The scope could not be passed beyond the anterior nostrils.

The CT scan of the paranasal sinuses showed almost complete opacification of all the paranasal sinuses with polypoid and mucosal thickening. There were areas within the opacification which appeared hyperdense, suggesting chronic impaction, the presence of fungus or haemorrhage. The maxillary osteomeatal complexes were obliterated. There was complete opacification of the nasal cavities with polypoid and mucosal thickening with a small area of patent airway in the inferior aspects bilaterally. Posteriorly, the polyps projected into the nasopharynx. Multiple areas of the walls of the frontal sinuses had become very thin. In certain areas, there was projection into the frontal intracranial fossa and into the bilateral orbits. There was expansion of the sinuses, bony dehiscences and focal erosions. In the left orbit, there was contact with the superior rectus muscle. The intraorbital extension produced left-sided proptosis. Intracranial extension produced mild indentation of the left frontal cortex.

The erosions and intracranial/intraorbital extensions prompted further clarification with an MRI study. MRI of the orbits also confirmed the intracranial and intraorbital extensions. Coronal T2WI showed a well-defined lobulated mass in the right ethmoid sinus, demonstrating central high signal intensity with a peripheral hypointense rim.

The imaging findings suggested sinonasal polyposis with bony erosions. The images do not show a clear destructive pattern but a remodelling pattern. There were no characteristics apart from the prolapse into intracranial/orbital compartments that could mimic malignancy.

Histopathology

FESS was done. The histopathology report was published as “bilateral oedematous nasal polyps with marked inflammation”. The right-sided polyp also showed areas of infarction and ulceration. There was no dysplasia or neoplasia. Features are suggestive of “Angiomatous Polyp”.

Sinonasal polyposis is a very common disease condition across the world. Inflammatory sinonasal polyps are classified into five variants: oedematous, glandular, fibrous, cystic, and angiomatous polyps [2].

Two theories have been hypothesised regarding the pathogenesis of angiomatous polyps [3]. The first theory is based on nasal polyps. Angiomatous polyp is a form of antrochoanal polyp vulnerable to vascular compromise in areas of anatomic constrictions. These areas are: (a) the ostial exit, (b) the posterior end of inferior turbinate, (c) posterior choana, and (d) the most dependent part in the nasopharynx. Subsequent venous infarction and neovascularisation of the polyp occurs, enabling repeat occlusion and infarction [5,6]. Another theory is based on haematoma in the maxillary antrum, which may be consequent to multiple causes such as trauma, vessel rupture, inflammatory tear or coagulopathy. Negative pressure, poor drainage and decreased air exchange in the maxillary antrum results in accumulation, organisation and fibrous degeneration of the haematoma. Reactive changes and neovascularisation follows gradually, forming an angiectatic polyp in the due course [7]. On microscopy, angiomatous polyp characteristically shows extensive vascular proliferation and angiectasis, resulting in venous thrombosis, and infarction [8].

The majority of the angiomatous polyps originate in the maxillary sinus [2]. They may expand into the nasal cavity, across the choana and into the nasopharynx [2].

The most frequent symptoms are nasal congestion, nasal discharge, headache, and epistaxis. Other symptoms include proptosis, diplopia, facial swelling, and auditory impairment. Progressive expansion of the angiomatous polyps can lead to bone erosion and disruption of the surrounding bony parts, causing swollen face, and proptosis. These symptoms are common to both benign and malignant pathologies.

Computed tomography (CT) of the paranasal sinuses is the radiologic investigation of choice for diagnosis of sinonasal lesions [9]. CT shows sinonasal bone thickening, hyperostosis, remodelling, dehiscence, erosion, or destruction. MR imaging provides further insights into the lesion. On T1WI, the lesion typically demonstrates heterogeneous hypointense signal intensity. On T2WI, the lesion shows high signal intensity surrounded by a peripheral hypointense rim, presumably a hemosiderin deposit indicative of old microhaemorrhage [4]. Linear hypointense septa may be present. Postcontrast MR images usually show homogeneously enhancing masses with unenhanced hypointense rim and septa. Dynamic contrast-enhanced MR imaging shows progressive enhancement of the lesion. The high-signal-intensity area surrounded by peripheral hypointense rim is a characteristic finding of angiomatous polyp [4]. DCE MR imaging provides very important diagnostic clues as well.

Magnetic resonance imaging (MRI) due to its high soft tissue resolution, is a better modality to detect and characterize orbital and intracranial invasion and/or possible complications. Definitive diagnosis requires adequate sampling and should be confirmed by histopathological examination [10].

Transnasal endoscopic removal is the best therapeutic option of choice [1]. It has good prognosis with low level of recurrence.

Conclusion

Angiomatous sinonasal polyp is a possible differential diagnosis in aggressive sinonasal lesions. The diagnosis can only be confirmed after histopathological examination.