Histopathology of sinonasal fungal disease.

1. To increase diagnostic yield, the otolaryngologist should convey suspicions of mycotic sinus disease to the pathologist. 2. Fungal cultures are a necessary adjunct to histopathologic identification. 3. Any sinonasal chronic inflammatory or granulomatous sinus process, or allergic process, may have a fungal etiology, even with negative GMS stains. 4. The diagnosis of sinonasal "inflammatory pseudotumor" should be accepted with some reservation, as it may represent an unrecognized sinonasal mycotic process. 5. Aspergillus spp. may be definitively identified histologically in sinonasal mycetomas and in invasive disease. When only fragments of thin septate hyphae, are found, one cannot assume they always belong to Aspergillus. 6. One must not assume that all wide "pleomorphic" hyphal fragments belong to Rhizopus or, for that matter, Zygomycetes. 7. Candida, Pseudoallescheria, Rhinosporidium and Cryptococcus are rare sinonasal pathogens that may also be positively identified morphologically.