Answer: Invasive fungal sinusitis, acute/fulminate

Histology: There is focal ulceration of the surface epithelium. Beneath the ulcer is a large geographic zone of necrosis. The necrosis is very bland, and there is a conspicuous absence of inflammatory cells, multinucleated giant cells, and nuclear debris. At high power, fungal forms are readily apparent on the routine hematoxylin and eosin stained slides. These hyphal forms are septated and demonstrate 45-degree angle branching. They are present within the area of tissue necrosis and extend into adjacent viable tissue.

Discussion: Beginning in the 1970s there has been a precipitous rise in the incidence of fungal sinusitis, largely as a result of heightened awareness as well as increasing vulnerability owing to immunosuppression. The specific type of fungal disease results from a complex interplay between the environmental load, the host immune status, and local tissue conditions. Four major types are recognized.

“Allergic fungal sinusitis” is a non-invasive form of fungal sinusitis that occurs primarily in young adults with long histories of asthma and nasal polyposis. Most have elevations of their total IgE levels and absolute eosinophil counts. Clinically, the affected sinus contains a firm rubbery and tenacious mucous material. A constant microscopic feature is the presence of so-called “allergic mucin” – eosinophilic or basophilic mucous material with embedded eosinophils, sloughed epithelial cells, cellular debris, and Charcot-Leyden crystals. Although fungal organisms may be identified in about half of these cases, the organisms are present in the allergic mucin and not within the tissues.

“Mycetoma” fungal sinusitis is an extramucosal fungal ball within a single sinus, usually the maxillary sinus. The host is typically healthy and immunocompetent, but there may be some history of prior trauma or some type of insult to the maxillary sinus. Because the fungus is non-invasive, simple curettage is usually curative, and systemic antifungal therapy is not indicated.

“Chronic indolent sinusitis” is an invasive form of fungal sinusitis in that there is penetration of the mucosa. In these patients, an obvious immune deficiency is not apparent. In contrast to more fulminant forms in immunocompromised patients, the disease is indolent in its progression. The disease is characterized by a relentless course that presents with chronic headache and facial swelling that may progress over months to years. Advanced progression may even give rise to visual impairment. Depending on the immune status of these patients, they are at risk for developing a fulminant form of invasive fungal sinusitis. Histologically, one of the major differences between fulminant and indolent fungal sinusitis is the associated host reaction. In contrast to the paucity of host reaction in fulminant forms of invasion, a granulomatous chronic inflammation characterizes chronic indolent sinusitis.

Fulminant sinusitis is usually seen in the immunocompromised host. Typically, these patients are profoundly neutropenic due to hematopoietic malignancies, or they are immunosuppressed. The fungi show a destructive and fulminant pattern of invasive growth, with progressive destruction of the sinuses and extension into the orbit and brain. Angiocentric invasion is common, and although there may be prominent tissue necrosis there is little in the way of a host reaction. Aspergillus and mucormycosis are the two most common pathogens, the most common setting for mucor being the diabetic patient in ketoacidosis. The mainstay of therapy for invasive forms of fungal sinusitis (chronic and fulminant) is aggressive surgical debridement and antifungal chemotherapy. Hyperbaric oxygen has also been advocated.