Diagnostic accuracy of morphologic identification of filamentous fungi in paraffin embedded tissue sections: Correlation of histological and culture diagnosis

Aims and Objectives: The aim was to investigate the correlation between histological and culture diagnosis of filamentous fungi. Materials and Methods: Tissue sections from biopsy samples stained with Hematoxylin and Eosin and special stains from samples of chronic invasive/noninvasive sinusitis and intracranial space occupying lesions during 2005-2011 diagnosed to have infection due to filamentous fungi were reviewed. The histopathology and culture diagnoses were analyzed for correlation and discrepancy. Results: There were 125 samples positive for filamentous fungi on biopsy. Of these 76 (60.8%) were submitted for culture and fungi grew in 30 (39.97%) samples. There was a positive correlation between histological and culture diagnosis in 25 (83.33%) samples that included Aspergillus species (16/19), Zygomycetes species (8/10) and dematiaceous fungi (1/1). The negative yield of fungi was more in Zygomycetes species (20/30) when compared to Aspergillus species (25/44). There was a discrepancy in diagnosis in 5/30 (16.67%) samples which included probable dual infection in two, and dematiaceous fungi being interpreted as Aspergillus species in three samples. Conclusion: Histopathology plays a major role in the diagnosis of infection due to filamentous fungi, especially when cultures are not submitted or negative. The discrepancy between histological and culture diagnosis was either due to dematiaceous fungi being interpreted as Aspergillus species or probable dual infection.