Sphenoid Sinus Fungus Ball Mimicking Sellar Neoplasm: A Case Report and Review of Diagnostic Challenges

Histopathologic classification of fungal diseases in the paranasal sinuses differentiates between invasive and non-invasive types based on the degree of mucosal involvement. This distinction is crucial as the treatment strategies and prognoses for each type vary significantly. Non-invasive diseases include saprophytic fungal infestation, allergic fungal rhinosinusitis, and fungal ball. The latter predominantly affects the maxillary and sphenoid sinuses of immunocompetent subjects. This report details an unusual case of a bulky sphenoid fungus ball initially misdiagnosed as a sellar neoplasm due to extensive skull base erosion. A 55-year-old female presented with headache and blurry vision, and imaging revealed a mass suggestive of a sellar tumor. MRI indicated a large sphenoid sinus mass extending into the Sella. The patient underwent endonasal endoscopic surgery, which revealed a fungus ball without mucosal invasion. Postoperative recovery was uneventful, with vision returning to normal. Histopathology confirmed the presence of Aspergillus fumigatus. This case underscores the diagnostic challenges posed by sphenoid sinus fungus balls, which can mimic sellar neoplasms due to their radiologic appearance and potential for skull base erosion. Prompt surgical intervention is crucial to prevent serious complications, including vision loss. Awareness of this condition can aid in differential diagnosis and appropriate patient management.