Fungi are the etiologic agents of a number of pathologies of the nasal cavities.9
Commonly, they are related to allergic rhinitis and thus may play some role in the development of chronic sinusitis and secondary complications from such. They also play a role in a number of other sinus pathologies that can be either noninvasive
Allergic Fungal Sinusitis
Allergic fungal sinusitis is the most common fungal disease of the sinuses. Clinically, patients with this disease are immunocompetent and may have concomitant asthma, allergic rhinitis, and nasal polyps.11
The disease is suspected after a protracted history of sinusitis that has been refractory to treatments for bacterial sinusitis. It may be secondary to either hyaline molds such as Aspergillus
species or to various dematiaceous molds.11
FIGURE 13.3 Mucus with numerous entrapped eosinophils.
Surgically collected specimens will grossly have tan-brown fragments of mucosa with green-brown mucoid material and have evoked for some the culinary impressions of cottage cheese and peanut butter.9
Histologically, samples show abundant mucus with entrapped eosinophils and Charcot-Leyden crystals (allergic mucus
) (Fig. 13.3
, eFig. 13.2).11
Although the fungal forms may be difficult to visualize with routine hematoxylin and eosin (H&E)-stained material, silver staining will show numerous hyphal fragments (Fig. 13.4
, eFig. 13.3). The hyphal fragments often branch at 45-degree angles and may have occasional conidia.13
Fragments of edematous and inflamed respiratory mucosa will also be present, showing changes consistent with chronic sinusitis, and should not contain organisms when viewed with special stains.
Sinus Mycetoma (Fungus Ball)
Sinus mycetomas most often occur in the maxillary sinuses of immunocompetent patients.9
Patients may present with headache, facial pain, nasal obstruction, or a perceived nasty odor, and patients may even present with new-onset seizure and may sometimes have concomitant nasal polyps and sinusitis. The disease is most often caused by Aspergillus fumigatus
Removed material will appear mucopurulent or cheesy.9
On sections, a dense collection of fungal elements will be seen, devoid of allergic mucus (Fig. 13.5
). Silver staining is rarely needed due to the abundance of the fungus (eFig. 13.4). The fragments of sinus tissue will show changes of chronic sinusitis, and fungi should not involve fragments of respiratory mucosa.
FIGURE 13.4 A silver stain shows occasional hyphal fragments.
Invasive Fungal Sinusitis
Invasive fungal sinusitis is a disease generally restricted to immunocompromised individuals, although rare instances are noted in which the disease has affected immunocompetent persons.9
Acute or fulminant invasive fungal sinusitis may present as a painless, black, nasal septal, or palatal
eschar. It is most often caused by fungi of the order Mucorales such as Rhizopus
but may also be caused by Aspergillus
species as well as dematiaceous species.
FIGURE 13.5 A fragment of a fungal ball.
FIGURE 13.6 Invasive fungi seen with silver stain.
Histologically, samples from patients with acute fungal sinusitis will show invasion of tissue by the hyphal elements often with involvement of vascular structures (Fig. 13.6
, eFig. 13.5).9
A secondary vasculitis and thrombosis with resultant hemorrhage and infarction may also be seen. Surrounding inflammation is often minimal, a reflection of the immunocompromised state of the patient. Some have suggested the use of in situ hybridization for the typing of the etiologic agents.19
Chronic invasive fungal sinusitis follows a more protracted course than acute invasive fungal sinusitis.9
Patients are immunocompromised usually secondary to diabetes mellitus or previous treatment with corticosteroids. The disease may be associated with decreased vision and ocular immovability (orbital apex syndrome). Some believe the lesion begins as a sinus mycetoma that eventually becomes invasive due to the immunocompromised state of the patient. The disease is most often secondary to infection by A. fumigatus
. As with acute invasive sinusitis, histologic sections show tissue and vascular invasion by hyphal elements, often with a limited inflammatory response.
Finally, paranasal granuloma or granulomatous invasive fungal sinusitis is a rare chronic fungal disease of immunocompetent patients that is associated with proptosis.9
The disease is secondary to infection by Aspergillus flavus
. Most reports of this lesion come from Sudan.
Histologically, tissue invasion is present which induces nonnecrotizing granulomatous inflammation with intermixed plasma cells. At the centers of these granulomata, a small amount of fibrinoid necrosis with eosinophils may be present. An associated vasculitis may also be seen.