Chronic Granulomatous Fungal Rhinosinusitis Mimicking a Giant Cell Tumor of the Maxilla: A Diagnostic Pitfall

Chronic granulomatous fungal rhinosinusitis is an uncommon form of invasive fungal sinusitis that typically affects immunocompetent individuals and often presents as a slowly progressive mass lesion, closely mimicking malignancy clinically and radiologically. We report the case of a 56-year-old woman who presented with a painless swelling over the left maxillary region for four months. She had a history of a similar lesion at the same site nine years earlier, which had been surgically excised elsewhere and diagnosed as a giant cell tumor of the maxilla. Magnetic resonance imaging revealed an expansile lesion involving the left maxillary sinus with extension into adjacent facial soft tissues and orbital contents, raising suspicion for a neoplastic process. Fine-needle aspiration cytology demonstrated numerous multinucleated giant cells, suggesting a giant cell tumor. The patient underwent total maxillectomy with orbital exenteration. Histopathological examination revealed well-formed non-caseating granulomas with central neutrophilic microabscesses forming suppurative granulomas. Slender septate fungal hyphae with acute-angle branching were identified on special stains, consistent with Aspergillus species. A final diagnosis of chronic granulomatous fungal rhinosinusitis was established. The patient was treated with intravenous voriconazole postoperatively and remains clinically stable on follow-up. This case highlights the importance of considering invasive fungal sinusitis in the differential diagnosis of destructive maxillofacial masses and underscores the critical role of histopathological evaluation in preventing misdiagnosis and unnecessary radical surgery.