Saprophytic fungal infestation: This is described as asymptomatic colonization of mucous crusts within the sino-nasal cavity, often in patients who have undergone previous sinus surgery. It has been predicted that this growth could lead to the formation of fungal ball [17].

Fungal ball: It is described as accumulation of dense conglomeration of fungal hyphae, without invasion, in one sinus cavity, usually the maxillary sinus, although the disease may affect other sinuses or rarely multiple sinuses [20]. It has been designated by various terms such as mycetoma, aspergilloma, and chronic non-invasive granuloma [17].

Fungus-related eosinophilic FRS that includes AFRS: The Bent and Kuhn [12] diagnostic criteria to diagnose AFRS are type I hypersensitivity, nasal polyposis, characteristic CT findings, presence of fungi on direct microscopy or culture, and allergic mucin containing fungal elements without tissue invasion. It is believed that eosinophilic rhinosinusitis (EMRS) and AFRS are differing manifestations of the same pathological process, with considerable overlap [19].

Irrespective of the controversy regarding classification of fungal sinusitis, it is extremely important to investigate all patients of chronic rhinosinusitis not responding to standard therapy and to identify the invasive versus the noninvasive form (allergic fungal sinusitis, fungal mycetoma). Aggressive surgery and antifungal treatment is required in the invasive forms while surgery alone may suffice in the non-invasive forms [21].