Fungus ball (mycetoma) is a dense, non-invasive mass of accumulated fungal hyphae within a paranasal sinus. It most commonly occurs in the maxillary sinus (75-90%) in immunocompetent individuals. It is generally unilateral and involves a single sinus. Hyperdense calcified material (metallic density foci) within the sinus on CT is the characteristic finding. The mucosa is intact with no invasion — bone destruction is not expected, although reactive bone sclerosis and mild sinus wall expansion may be seen due to chronic pressure effect. Aspergillus fumigatus is the most common causative organism. Treatment is removal via endoscopic sinus surgery; antifungal therapy is not required.
Age Range
40-80
Peak Age
60
Gender
Female predominant
Prevalence
Uncommon
Fungus ball develops when inhaled fungal spores colonize within the sinus and over time form a dense mass of fungal hyphae. Since the immune system is intact, fungal organisms cannot penetrate the mucosa — the infection remains confined to the sinus lumen. Fungal hyphae accumulate heavy metals such as calcium, iron, and manganese through metabolic processes; these metallic accumulations are responsible for the characteristic hyperdense/calcified appearance on CT. Sinus ostium obstruction (anatomic variant, polyp, prior surgery) is a predisposing factor — mucociliary clearance is impaired in the obstructed sinus and fungal growth is facilitated. The chronic fungal mass exerts pressure on the sinus wall leading to reactive bone remodeling (sclerosis, mild expansion) but does not cause bone destruction. Secondary inflammatory thickening may develop in adjacent mucosa.
Irregular, heterogeneous, punctate or clustered hyperdense calcified/metallic density foci within a single sinus is the most characteristic and pathognomonic CT finding of fungus ball. These calcifications can range from 100 HU up to metallic density (>1000 HU). Calcium, iron, and manganese compounds accumulated through metabolic processes of fungal hyphae are responsible for these high densities. This finding distinguishes non-invasive fungal sinusitis from the invasive form and from bacterial sinusitis. CT alone is generally sufficient for diagnosis — additional imaging is rarely needed.
On non-contrast CT, hyperdense (100-200+ HU), punctate or clustered calcifications/metallic density foci are seen within the sinus lumen. This hyperdense material consists of calcium, iron, and manganese compounds accumulated by fungal hyphae through metabolic processes. Calcifications are typically irregular, heterogeneous, and clustered — different from homogeneous calcification. In some cases, calcifications are very dense and can create metallic artifact. Hyperdense material may fill the sinus completely or partially; low-density mucous retention may be present around it. This finding is nearly pathognomonic for fungus ball diagnosis and is usually sufficient on its own.
Report Sentence
Irregular hyperdense calcifications/metallic density foci are noted within the left maxillary sinus lumen, consistent with fungus ball (mycetoma).
The chronic pressure and inflammatory effect of the fungus ball leads to reactive bone sclerosis and thickening of the sinus walls. This sclerosis is homogeneous and smooth in contour — irregular bone destruction is not expected (if destruction is present, invasive fungal sinusitis should be considered). The presence of bone sclerosis indicates a chronic process and differs from normal bone structure in acute sinusitis. In some cases, mild expansion/remodeling of the sinus wall may also be seen, but this expansion is not as prominent as in mucocele. The degree of bone sclerosis correlates with disease duration.
Report Sentence
Reactive bone sclerosis and mild thickening is noted in the left maxillary sinus walls, assessed as changes due to the pressure effect of chronic fungal ball.
On MRI T2-weighted sequences, the fungus ball appears markedly hypointense ('T2 signal void' or 'T2 blackout'). This low signal results from the strong T2-shortening effect of paramagnetic metallic ions (iron, manganese, calcium) accumulated by fungal hyphae and low water content of desiccated material. T2 hypointensity can be so prominent that it may be confused with air — T1 sequences are used for differentiation (air produces no signal on T1 either, while fungal material shows low-intermediate T1 signal). The surrounding inflammatory mucosa appears T2 hyperintense and creates sharp contrast with the fungal mass. Gradient echo (GRE/SWI) sequences amplify the susceptibility effect and show the hypointensity even more prominently.
Report Sentence
Material showing markedly hypointense signal within the left maxillary sinus lumen on MRI T2-weighted sequences is noted, demonstrating T2 blackout finding consistent with fungus ball.
Fungus ball shows variable signal on T1-weighted sequences — generally low-intermediate signal intensity but may contain focal hyperintense areas depending on protein and metallic content. Paramagnetic metallic compounds (manganese, natural gadolinium) show T1-shortening effect and can produce bright signal on T1. On contrast T1, the fungal mass does not enhance (avascular) but surrounding mucosa shows intense enhancement — this pattern reveals the contrast between inflammatory mucosa and non-viable fungal material. The border between enhancing mucosa and non-enhancing fungal mass is typically sharp.
Report Sentence
Non-enhancing intraluminal material and intensely enhancing peripheral mucosa is noted in the left maxillary sinus on contrast T1 MRI, consistent with avascular fungal mass and reactive mucosal inflammation.
Fungus ball characteristically involves a single, unilateral sinus — most commonly the maxillary sinus (75-90%), less frequently the sphenoid sinus. Within the opacified sinus, low-density (10-30 HU) mucous retention may be seen alongside hyperdense material. The sinus is usually completely or subtotally opacified with minimal or no residual air. Unilateral involvement and single sinus limitation distinguishes from diffuse polyposis and bilateral sinusitis forms. Sphenoid fungus ball is clinically more important because it carries complication risk due to proximity to the optic nerve and internal carotid artery.
Report Sentence
The left maxillary sinus is subtotally opacified with heterogeneous density material within the lumen (low-density retention + hyperdense calcified foci); findings are consistent with fungus ball.
Ultrasonography plays a limited role in paranasal sinus evaluation but in fungus ball, visibility of the posterior wall echo indicates intrasinus material. Fungal calcifications may appear as hyperechoic foci within the sinus and may demonstrate posterior acoustic shadowing (shadow behind calcifications). However, CT and MRI are far superior to ultrasonography in diagnosing fungus ball. Ultrasonography can be used for screening purposes particularly in pediatric patients or pregnant women; hyperechoic intrasinusoidal material finding indicates further evaluation with CT.
Report Sentence
Posterior wall echo is visible on left maxillary sinus ultrasonography with material containing hyperechoic foci within the sinus; further evaluation with CT is recommended.
Criteria
Most common form (75-90%). More frequent in immunocompetent, middle-aged to elderly women. Usually incidental or presents with mild facial pain/nasal discharge.
Distinct Features
Hyperdense calcified material in maxillary sinus, reactive bone sclerosis on CT. Dental pathology relationship should be investigated (prior root canal treatment may contain ZnO — endodontic material can predispose to fungal colonization).
Criteria
Rarer (5-10%) but clinically more important. High complication risk due to proximity to optic nerve and internal carotid artery. May present with headache and visual disturbance.
Distinct Features
Sphenoid sinus opacification + hyperdense material on CT. Bone erosion (lateral recess — internal carotid artery proximity) should be carefully evaluated. MRI superior to CT in showing carotid artery and optic nerve relationship.
Criteria
Rare location (3-5%). Ethmoid sinus anterior and posterior cells may be involved separately. Frontal sinus involvement is rarest.
Distinct Features
Orbital complication potential in ethmoid sinus fungus ball (lamina papyracea proximity). Intracranial complication risk in frontal sinus involvement due to anterior cranial fossa proximity. May produce early symptoms due to small sinus volume.
Distinguishing Feature
Invasive fungal sinusitis shows bone destruction, mucosal non-enhancement (devitalized tissue), and extrasinus extension — in fungus ball, bone is intact (may be sclerotic), mucosa enhances, and disease is confined to the sinus lumen. Immunosuppression clinical context suggests invasive form.
Distinguishing Feature
AFS involves multiple sinuses (bilateral), sinus expansion is prominent with hyperdense mucin and bone remodeling. Fungus ball is confined to a single sinus and sinus expansion is not prominent. Atopy and asthma association is expected in AFS.
Distinguishing Feature
Hyperdense calcified material within the sinus is not expected in chronic sinusitis — opacification consists of low-moderate density (10-40 HU) secretions. Bone sclerosis can be seen in both. Intraluminal hyperdense foci (>100 HU) in fungus ball are distinguishing.
Distinguishing Feature
Dental pathology adjacent to sinus floor (periapical abscess, implant, oroantral fistula) is expected in odontogenic sinusitis. Hyperdense material may be close to dental source (endodontic cement) but differs from the diffuse calcification pattern of fungus ball. Both conditions can coexist — dental treatment material can predispose to fungal colonization.
Urgency
routineManagement
surgicalBiopsy
Not NeededFollow-up
Endoskopik sinüs cerrahisi ile çıkarım sonrası antifungal tedavi gerekmez. Rekürrens nadir. Sfenoid fungus ball'da postoperatif kontrol önerilir.Fungus ball treatment is complete removal via endoscopic sinus surgery (ESS). Antifungal therapy is not required because the infection is non-invasive and surgical removal is curative. Mucosal integrity is preserved during surgery; only the fungal mass is debrided and the natural ostium is widened. Recurrence rate is low (5-10%). Postoperative follow-up is done with endoscopic examination at 1-3 months. In sphenoid fungus ball, optic nerve dehiscence and internal carotid artery dehiscence should be evaluated by CT before surgery — surgical complication risk should be reported. If dental pathology is present, simultaneous dental treatment should be planned.
Treatment of fungus ball is surgical removal (FESS). Antifungal therapy is not required as there is no invasion. Prognosis is excellent. Previous dental procedure history may be present (maxillary sinus).