Allergic fungal sinusitis is a histopathologic diagnosis; paranasal mucocele is not.

Allergic fungal sinusitis has been known to pathologists for two decades. During this time, multiple articles have stressed that the condition continues to be underdiagnosed. This is true, but it can also be overdiagnosed. This means that series of cases used for clinical studies usually are "contaminated" with cases that are misdiagnosed. Because the condition is often quite problematic to control, determination of the best treatment regimens is important. This will be dependent on clinical studies including only correctly diagnosed cases for study. This article discusses the steps toward making the correct diagnosis.