Histological classification of fungal sinusitis

Four distinct histologic categories of fungal sinusisits have been recognised. This classification goes a long way in deciding the optimal management modality in patients suffering from this condition.

1. Allergic fungal sinusitis
2. Non invasive fungal colonization (fungal ball)
3. Chronic invasive fungal sinusitis
4. Acute fulminant fungal sinusitis

Acute fulminant fungal sinusitis is commonly seen in immunocompromised / diabetic patients. This can really be fatal and hence need to be treated aggressively with systemic antifungal agents.

Allergic fungal sinusitis does not require antifungal therapy but should be treated aggressively for the underlying allergy. Aim of treating these patients aggressively is to reduce the incidence of recurrence rates. After surgical removal of the disease these patients should be treated with corticosteroids with simultaneous montoring of serum IgE levels. This also reduces clinical symptoms. Current management modalities also include antileukotriene agents.

Allergic fungal sinusitis can be suspected if allergic mucin is present in the specimen. This mucin is a special type and could be green, brown or black in color. The material present has a consistency of that of clay and the cut surface appears laminated. Microscopically allergic mucin appears eosinophilic on H&E stain. There is also associated presence of charcot leyden crystals and eosinophils. The mucosal tissue demonstrated changes consistent with that of inflammatory polyposis.

Histological diagnosis of non invasive fungal sinusitis is really easy as fungal organims can be clearly seen in abundance under H&E.

Acute fulminant sinusitis is characterised by tissue invasion by fungal organism. In this type angioinvasion is really common in contrast chronic invasive fungal sinusitis is characterised by tissue invasion and formation of granulation tissue.

Currently one more entity has been added.

EMRS: (eosinophilic mucin rhinosinusitis)

This entity is characterised by the presence of allergic mucin but fungal hyphae is not evident. Fungal cultures too turn out to be negative.