Microbiological and Radiological Characteristics of Paranasal Sinus Fungus Ball: a retrospective analysis of 235 cases.

Paranasal sinus Fungus Ball (FB) is the most common non-invasive mycotic rhinosinusitis. It most frequently affects the maxillary and sphenoidal sinuses and the treatment of choice is Endoscopic Sinus Surgery (ESS). Although this pathology has been widely investigated throughout the years, some questions still remain unanswered. This study concentrates on assessing radiological and microbiological characteristics by examining a large number of cases treated in our centre. 235 cases of FB that underwent ESS in Fondazione I.R.C.C.S. Policlinico San Matteo di Pavia in the period comprised between January 2000 and May 2020 were collected. The surgical report, microbiological culture, histological report and preoperative Computed Tomography were analysed. FB was confirmed to affect more commonly the female population (68.22%). The maxillary (69.78%) and sphenoidal sinuses (27.23%) were the most frequent localizations. Interestingly, the microbiological reports showed different growth patterns as positive cultures from maxillary FB were reached in 21.52% of cases, while from sphenoidal FB in 45.76%. Different mycotic populations were found: Aspergillus fumigatus was isolated in 33 FB specimens, of which 63.3% in the maxillary sinus, while Aspergillus flavus was isolated in 10 specimens, of which 80% in the sphenoid sinus (p=0.017 and p=0.039 respectively). Radiologically, heterogeneous soft tissue density at sinus cavity (p=0.029) was more represented in patients with positive culture. This study analysed a large population and demonstrated differences in the growth pattern and subpopulation of fungi between differently localized FB, underlining a new characteristic of this pathology.