Metagenomic next-generation sequencing for pathology-suspected fungal infections at rare anatomical sites: a case series

OBJECTIVE: Histopathology for suspected fungal infections lacks species-level identification and is prone to morphological mimics. The utility of metagenomic next-generation sequencing (mNGS) at rare anatomical sites is underexplored. METHODS: We retrospectively analyzed 10 cases with histopathology suggestive of fungal infection at rare sites (brain, cardiac valve, bone, etc.). All underwent mNGS testing on formalin-fixed paraffin-embedded samples. RESULTS: mNGS detected fungal DNA in 8/10 cases (80%), providing species-level identification (e.g., Cryptococcus, Candida, Fusarium, Rhizopus, Histoplasma). Polymicrobial infections were identified in 70%. mNGS corrected two misdiagnoses: one confirmed neurocysticercosis; another revealed only bacteria in a suspected fungal lesion. Antimicrobial resistance genes (ErmB) were identified in two cases. CONCLUSION: mNGS enhances diagnostic precision at rare sites by enabling species identification, uncovering polymicrobial infections, and correcting morphological misdiagnoses, supporting targeted therapy.