Allergic fungal mucin, as depicted in the images below normally is first encountered at surgery. Therefore, recognition of its presence is the initial step in establishing an accurate diagnosis of allergic fungal sinusitis (AFS). Realizing that mucin, rather than paranasal sinus mucosa, demonstrates the histologic appearance consistent with allergic fungal sinusitis (AFS) is important. Examination of mucosa and polyps obtained from involved paranasal sinuses reveals findings consistent with the inflammation of a chronic inflammatory process and should be performed to exclude fungal invasion. Once mucin is collected, culture and pathologic examination are undertaken.
Left middle meatus with suctioning of thick allergic mucin from the ethmoid bulla in the center of the picture; the end of the suction is in the inferior portion of the picture.
The viscosity of a thick allergic mucin being suctioned from the nasal cavity and vestibule in a patient with allergic fungal sinusitis.
Initially described by Millar and Lamb and Katzenstein et al, histologic examination of allergic mucin reveals a constellation of characteristic findings. [22] Branching noninvasive fungal hyphae are identified within sheets of eosinophils and elongated eosinophilic bodies (Charcot-Leyden crystals), which represent the product of eosinophilic degradation. Use of various histologic staining techniques helps to identify the variety of components within allergic fungal mucin. Hematoxylin and eosin (H&E) staining accentuates the mucin and cellular components of allergic fungal mucin. Using this stain, background mucin often takes on a chondroid appearance, while eosinophils and Charcot-Leyden crystals are heavily stained and become easily detectable.
Fungi fail to stain using this technique and therefore may be difficult to identify. The presence of fungi may be implicated on H&E stain by the resulting negative image against an otherwise stained background. However, fungal hyphae and elements are often rare, scattered, and fragmented within allergic mucin, rendering identification difficult unless specific histologic stains are used. Fungal elements are recognized for a unique ability to absorb silver. This property is the basis for various silver stains, such as the Grocott-Gomori methenamine silver (GMS) stain, which turns fungi black or dark brown. The use of a fungal stain complements the findings of initial H&E stain and is extremely important in the identification of fungi.
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Left middle meatus with suctioning of thick allergic mucin from the ethmoid bulla in the center of the picture; the end of the suction is in the inferior portion of the picture.
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The viscosity of a thick allergic mucin being suctioned from the nasal cavity and vestibule in a patient with allergic fungal sinusitis.
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View just inside the nasal vestibule showing diffused polyposis extending into the anterior nasal cavity and vestibule; the septum is on the right, and the right lateral vestibular wall (nasal ala) is on the left. The polyps all are in the center. The polyps almost hang out of the nasal vestibule.
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A 15-year-old boy with allergic fungal sinusitis causing right proptosis, telecanthus, and malar flattening; the position of his eyes is asymmetrical, and his nasal ala on the right is pushed inferiorly compared to the left.
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A 9-year-old girl with allergic fungal sinusitis displaying telecanthus and asymmetrical positioning of her eyes and globes.
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Coronal CT scan showing extensive allergic fungal sinusitis involving the right side with mucocele above the right orbit and expansion of the sinuses on the right.
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Typical view of a middle meatus in a patient with allergic fungal sinusitis with expansion of the ethmoid complex and extension of the middle turbinate more inferiorly. This is a postoperative view.
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Coronal CT scan showing typical unilateral appearance of allergic fungal sinusitis with hyperintense areas and inhomogeneity of the sinus opacification; the hyperintense areas appear whitish in the center of the allergic mucin.
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Coronal MRI showing expansion of the sinuses with allergic mucin and polypoid disease; the hypointense black areas in the nasal cavities are the actual fungal elements and debris. The density above the right eye is the mucocele. The fungal elements and allergic mucin in allergic fungal sinusitis always look hypointense on MRI scanning and can be mistaken for absence of disease.
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Immediate postoperative 30° angled view showing the complete removal of polyps with a widened frontal sinus recess superiorly and widened ethmoid cavity in the mid portion. The middle turbinate is on the right, pushed against the septum. The lateral nasal wall is on the left.
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Fungal ball in the right maxillary sinus.
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Fungal debris being removed from the ethmoid complex. A suction device is seen in the right lower corner of the picture.
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Allergic mucin, fungal debris, and polyps are shown after removal from the patient. The scale is in inches.
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Coronal CT scan showing the postoperative view following removal of disease after significant disease recurred on both the right and left sides of the nasal cavity and sinuses; mild mucosal thickening of all involved sinuses is present, with some moderate thickening of the left maxillary sinus. All disease, even the lateral mucocele, was removed or drained endoscopically.
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Two-week postoperative endoscopic picture showing polypoid thickening already in the ethmoid cavities while the patient was still on tapering steroids; on the left is the lateral nasal wall. The right shows the middle turbinate next to the septum.
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A polypoid recurrence in the center of the ethmoid cavity. The septum is on the left.
