Granulomatous invasive fungal sinusitis

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Granulomatous invasive fungal sinusitis, sometimes termed granulomatous invasive fungal rhinosinusitis, is a form of invasive fungal sinusitis. Reports describing the imaging findings have been uncommon.

Epidemiology

It is rare and been mainly reported in Sudan, India, Pakistan and sometimes in the United States .

Unlike other forms of invasive fungal sinusitis (which affect only immunocompromised patients) granulomatous invasive fungal rhinosinusitis typically affects immunocompetent patients.

Clinical presentation

This disease presents with a focal expanding granulomatous mass arising from the sinonasal region, locally aggressive, destroying adjacent structures.

Clinical presentation is mainly due to the mass effect, with possible nasal obstruction or proptosis. If there is intracranial invasion, it tends to have scarce symptoms due to the slow growth. The disease often presents late, at advanced stages, due to the initial paucity of symptoms.

Pathology

Granulomatous invasive fungal rhinosinusitis is usually confirmed on the basis of clinical and histopathologic findings where there is non-caseating granuloma formation and fibrosis. It is usually caused by Aspergillus flavus.

Affected individuals are generally immunocompetent (unlike other forms of invasive sinusitis, which affect mainly immunocompromised individuals).

Radiographic features

Imaging shows a large expansive mass with bone destruction and invasion of adjacent structures including orbits, nasal cavity and cranial base.

CT optimally demonstrates the degree of bone destruction. The mass is typically intrinsically hyperdense, with homogenous contrast enhancement.

MRI demonstrates the same intense pattern of intense, homogenous enhancement. The most salient MRI finding is a characteristic T2 hypointensity, along with peripheral foci of susceptibility, due to the deposition of paramagnetic elements. DWI may show a “T2-blackout” effect secondary to the marked T2 hypodensity, which may limit the value of diffusion sequences. Often described are foci of enhancing parenchyma representing cerebritis, in the region of the brain immediately adjacent to the solid lesion .

Treatment and prognosis

There is scarce evidence regarding optimal management and follow up in the literature. However, generally initial conservative surgical excision of the mass is generally indicated, followed by medical treatment with antifungal agents (itraconazole/voriconazole), which appear to decrease the degree of disease relapse.

Prognosis is generally good, especially if there is no intracranial invasion.

Post-surgical relapse is common, especially if antifungal therapy is not established .

Differential diagnosis

It may be difficult to differentiate from a malignant lesion invading into paranasal sinuses, orbital soft tissues, infratemporal fossa and/or skull base :

  • sinonasal squamous cell carcinoma: often similar in appearance should always be considered in sinonasal malignancy
  • sinonasal adenoid cystic carcinoma: mostly affects maxillary sinus and nasal cavity; very high propensity for perineural tumor spread
  • sinonasal adenocarcinoma: more aggressive, heterogeneous enhancement pattern; classically described in wood-workers (intestinal subtype)
  • sinonasal undifferentiated carcinoma (SNUC): mostly affects ethmoid and nasal cavity; early nodal metastases
  • sinonasal lymphoma: mainly affects paranasal sinuses and simulates benignity, with frequent bone remodeling more than destruction; homogeneous contrast-enhancement with homogeneous diffusion restriction, with scarce or no necrosis, are characteristic
  • sinonasal melanoma: mainly affects the inferior nasal fossa; lesions are characteristically hypervascular and hemorrhagic; can sometimes simulate benignancy, with frequent bone remodeling instead of destruction; if the tumor is the melanotic subtype, they can have a slight characteristic T1 hyperintensity
  • esthesioneuroblastoma: centered on the cribriform plate, with characteristic dumbbell shape affecting ethmoid sinuses inferiorly and invading anterior cranial fossa superiorly; often show adjacent bone hyperostosis, bone remodeling and nasal cavity expansion; intracranial tumor-margins often show characteristic peripheral T2-hyperintense cysts
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