INTRODUCTION
Fungi are recognized as etiologic agents in a wide range of disease states of the nose and paranasal sinuses. The International Society for Human and Animal Mycology divides fungal rhinosinusitis (FRS) into invasive and non-invasive types based on histopathologic evidence of fungus penetrating host tissue.1 The sinus fungal ball (SFB), usually found in the maxillary sinus (MSFB), is the most frequently encountered form of non-invasive FRS in clinical practice.1 Several studies have reported an increasing incidence of SFB over the past few decades in Asia.2-5Yoon et al. reported annual incidence of SFB remained below 5% until 2001, but increased to over 10% since 2011 in Korea.4Liu et al. found out the incidence of SFB in the last 5 years was significantly greater than that in the first 5 years during the 10-year study period (2008-2017) in China.5 Studies have also shown that SFB mostly occurs in older individuals, with a female predominance. The average age at presentation has been reported to be 49 to 61.1 years, with women accounting for 60.1% to 76.7% of cases.4-8
In addition, an increasing number of researchers have suggested that adjacent odontogenic infection increases the risk of MSFB owing to the close relationship between the antral teeth and sinus floor.9 Furthermore, endodontic treatment on maxillary teeth is considered to be a significant risk factor for the development of MSFB.10 The sinus mucosa may be damaged by chemical and physical trauma as a result of endodontic treatment, causing inflammation. Since maxillary odontogenic pathologies and endodontic procedures increase in frequency with aging, the role of odontogenic etiologies in MSFB may explain the predominance of this condition in the older population.6,11
Endoscopic sinus surgery (ESS) for eradicating SFB usually achieves good outcomes and has been considered as the standard treatment.7 Therefore, early diagnosis of SFB is important to avoid unnecessary medical therapy and treatment delays. Intralesional hyperdensity (IH), included calcifications with a nodular or linear shape, indicate the presence of heavy metal deposition within fungal hyphae12,13 and has been the most specific characteristic of SFB on computed tomography (CT) scan images. In the literature, the prevalence of IH on CT images of MSFB ranges from 66% to 82%.5,8,14 However, for those without IH on CT scan images, the diagnosis of MSFB continues to be a challenge. Our previous study proposed an algorithm to improve the identification of MSFB based on the findings of pre-operative CT scans.15 In this study, we retrospectively investigated patients with SFB who underwent ESS in our institute between 2005 and 2018. The aims of this study were to elucidate the clinical characteristics of MSFB and to increase pre-operative identification of the presence of MSFB, especially in those without IH on CT scan images.