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Fontana-Masson stain in fungal infections
Kelly Leigh West1, Alan D Proia2, Puja Kumari Puri3
1Ball Dermpath, Greensboro, North Carolina.
Background:
Fontana-Masson (FM) staining is a histopathology technique used to identify dematiaceous fungi. The result often guides initial species identification and antifungal treatment; however, there is evidence that nondematiaceous fungi might react with this stain. Few studies in the current literature address this issue.
Objective:
Our aim was to classify the FM staining patterns of common fungal pathogens for use by pathologists attempting to accurately identify fungi on histopathologic examination.
Methods:
In total, 132 cases of culture proven mycoses were identified. We stained tissue with 2 different FM protocols and recorded the intensity and distribution of results.
Results:
There was variability in staining, and many nondematiaceous fungi showed positivity, including Zygomycetes, Aspergillus, and Fusarium spp.
Limitations:
The study was limited by the number of cases. Of 132 cases identified, 112 cases had adequate tissue left after sectioning deeper into the block.
Conclusion:
Nondematiaceous fungi frequently stained positive with FM. The course of treatment should not be based on the result of this stain alone. Histopathology should be examined in multiple tissue sections, and therapy should be determined on the basis of clinical context and culture results.
Insights
Fontana-Masson (FM) staining can falsely identify nondematiaceous fungi, impacting fungal diagnosis. Relying solely on FM staining for antifungal treatment is not recommended; clinical context and cultures are crucial.
Area of Science:
- Medical Mycology
- Histopathology
- Diagnostic Microbiology
Background:
- Fontana-Masson (FM) staining is a histopathology method for identifying dematiaceous fungi.
- Current literature lacks comprehensive data on FM staining of nondematiaceous fungi.
- Accurate fungal identification is critical for guiding antifungal therapy.
Purpose of the Study:
- To classify Fontana-Masson staining patterns of common fungal pathogens.
- To aid pathologists in accurate fungal identification on histopathologic examination.
- To assess the reliability of FM staining for fungal species differentiation.
Main Methods:
- Retrospective analysis of 132 culture-proven mycosis cases.
- Application of two distinct Fontana-Masson staining protocols to tissue samples.
- Recording and analysis of staining intensity and distribution patterns.
Main Results:
- Variability in FM staining observed across fungal species.
- Significant positivity of FM stain in nondematiaceous fungi, including Zygomycetes, Aspergillus, and Fusarium spp.
- Demonstrated potential for false-positive results in fungal identification.
Conclusions:
- Nondematiaceous fungi frequently exhibit positive FM staining.
- Fontana-Masson staining alone is insufficient for definitive fungal diagnosis and treatment decisions.
- Integrated approach using multiple tissue sections, clinical context, and culture results is essential for accurate antifungal therapy.
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