Erosive and Expansile Lesion of the Maxillary Sinus by a Sinus Fungus Ball Mimicking Malignancy

Abstract

Paranasal sinus fungus balls are a form of fungal infection, mostly associated with the maxillary sinus. They are noninvasive lesions that usually develop in immunocompetent individuals with no predisposing factors. Fungus balls are mostly related to Aspergillus species, whereas Mucor species have been rarely reported. Transformation of a fungus ball into an invasive mycosis may commence when the patient becomes immunosuppressed. It is of clinical importance to distinguish fungus balls from common sinusitis, neoplasia, hemorrhage, and other conditions. Histopathological investigation reveals the presence of nonseptate hyphae, whereas cultures often fail to detect Mucor species. Magnetic resonance imaging (MRI) is more sensitive than computed tomography (CT) scan in diagnosing fungal sinusitis, but there is no clear superiority of one imaging modality over the other. CT remains the method of choice. We present a case of a Mucor fungus ball of the maxillary sinus that transformed into an erosive noninvasive Mucor mycosis in patient with concomitant oral cancer. Diagnostic reasoning and difficulties in radiological diagnosis are being discussed.