Abstract Objective: To demonstrate the clinical, radiological and diagnostic pitfalls of managing an isolated frontal sinus fungus ball, and to compare with the literature. Material and methods: Retrospective analysis of two cases and literature review. Results: Isolated frontal sinus fungus ball is a rare cause of frontal sinus disease. We present two cases of isolated frontal sinus fungus ball which pre-operatively were suspected to be either a tumour or a mucocele. In both cases, cheesy, clay-like material was found intra-operatively within the frontal sinus, suggesting a fungus ball. Effective treatment included surgical debridement via an exclusively endoscopic or an external approach, variously. Final histopathological and mycological analysis revealed Aspergillus fumigatus. A literature review revealed 20 reported cases of isolated frontal sinus fungus ball, confirming the low prevalence of the disease. Conclusions: Frontal sinus fungus ball should be considered in the differential diagnosis of chronic, nonspecific forehead symptoms. To evaluate the underlying disease, computed tomography scans should first be performed, followed by magnetic resonance imaging if malignancy is suspected. It is essential to be aware of the possibility of an atypical fungus ball appearance on computed tomography and magnetic resonance imaging scans. If bony destruction and calcification coexist on radiological images, then endoscopic biopsy is an indispensable part of the diagnostic procedure, and should be performed to collect material for both histological and mycological analysis, and to aid surgical planning. In cases of sinus fungus ball, an endoscopic approach for biopsy may be curativ
