Immunohistochemical dissimilarity between allergic fungal and nonfungal chronic rhinosinusitis

Diagnosis of allergic fungal rhinosinusitis (AFRS) is complicated because of the presence of fungi on mucosal surfaces of sinonasal passages. The objectives of this study were to define, using immunohistochemistry, lymphocyte populations associated with noninvasive fungal-related chronic rhinosinusitis (CRS; AFRS and FBs [FB]) relative to CRS with nasal polyposis (CRSwNP) and CRS without nasal polyposis (CRSsNP) as a means of diagnosing different forms of CRS.

Sinus CT scans, nasal endoscopy scores, and the presence of eosinophilic fungal mucin or FBs were used to prospectively define patient groups with CRS who had failed medical treatment and were undergoing endoscopic sinus surgery. Four patient groups were identified: AFRS, FB, CRSwNP, and CRSsNP. Tissue specimens were studied and graded for histopathological changes. Immunophenotyping of mucosal lymphocytes was performed using anti-CD3, -CD20, -CD4, -CD8, -CD56, and -perforin antibodies.

Nasal polyposis scores were similar between AFRS and CRSwNP. Radiological changes associated with AFRS can also be present in CRSwNP, e.g., heterogenicity in 9/30 (30%), expansion in 25/30 (83%), and bony attenuation of the ethmoid trabeculae in 19/30 (63%). Different grades of basement membrane thickness, edema, and fibrosis were observed. In both types of noninvasive fungal rhinosinusitis, CD3+ T lymphocytes were most commonly identified. In cases of AFRS, most T cells were CD8+ (p < 0.001). In FB cases, CD4+ lymphocytes were dominant (p < 0.001). In nonfungal CRS cases, CD20+ lymphocytes (B lymphocytes) predominated (p < 0.001).

Although CT scans and histological examination can assist the diagnosis of rhinosinusitis, tissue immunophenotyping can be used in defining different types of fungal and nonfungal CRS cases.