OBJECTIVETo compare the differences in clinicopathologic features of invasive fungal rhinosinusitis caused by Aspergillus and Mucorales, and to discuss the pathogenesis of tissue injury induced by these two kinds of fungi.

METHODSThe clinical and pathologic features of 19 patients with invasive fungal rhinosinusitis due to Aspergillus (group A) and 16 patients with invasive fungal rhinosinusitis due to Mucorales (group M) were retrospectively reviewed. HE, PAS and GMS stains were performed on all the paraffin-embedded tissues. The diagnosis was confirmed by histologic examination and microbiological culture results.

RESULTSAmongst the group A patients, the clinical course was acute in 4 cases and chronic in 15 cases. Thirteen cases had underlying predisposing conditions, including diabetes (number = 4), malignant tumor (number = 5), history of trauma (number = 1) and radical maxillary sinus surgery (number = 3). Follow-up information was available in 13 patients. Seven of them died, 4 due to fungal encephalopathy and 3 due to underlying diseases. Amongst the group M patients, the clinical course was acute in 14 cases and chronic in 2 cases. Fourteen cases had underlying predisposing conditions, including diabetes (number = 8), malignant tumor (number = 5) and history of wisdom tooth extraction (number = 1). Follow-up information was available in 14 patients. Four of them died of fungal encephalopathy. There was significant difference in clinical onset between the two groups (P = 0.01). There was however no difference in terms of underlying predisposing conditions and disease mortality. Histologically, the microorganisms in group A patients formed fungal masses and attached to the mucosal surface, resulting in necrotic bands (11/19). Epithelioid granulomas were conspicuous but multinucleated giant cells were relatively rare. Deep-seated necrosis, granulomatous inflammation against fungal organisms (3/19) and vasculitis with thrombosis (4/19) were not common. On the other hand, large areas of geographic necrosis involving deep-seated tissue could be seen in group M patients (13/16). Isolated multinucleated giant cells were commonly seen. Granulomatous inflammation against fungal organisms were identified (16/16). Vasculitis and thrombosis were also observed (10/16).

CONCLUSIONSThe invasiveness of Mucorales is remarkable; and when it causes invasive fungal rhinosinusitis, the clinical course is often acute and large areas of tissue necrosis can be seen. The invasiveness of Aspergillus in tissue is relatively mild. Granulomas are more common and the disease often runs a chronic clinical course. There is however no significant difference in long-term mortality. The pathogenesis may be related to the different components of the fungi.