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Comparison Approach for Identifying Missed Invasive Fungal Infections in Formalin-Fixed, Paraffin-Embedded Autopsy
Sota Sadamoto1,2, Yurika Mitsui3, Yasuhiro Nihonyanagi1
1Department of Surgical Pathology, Toho University School of Medicine, Tokyo 143-8541, Japan.
Abstract:
Invasive fungal infection (IFI) has a high mortality rate in patients who undergo hematopoietic stem cell transplantation, and it is often confirmed by postmortem dissection. When IFI is initially confirmed after an autopsy, the tissue culture and frozen section are challenging to secure, and in many cases, formalin-fixed, paraffin-embedded (FFPE) samples represent the only modality for identifying fungi. Histopathological diagnosis is a useful method in combination with molecular biological methods that can achieve more precise identification with reproducibility. Meanwhile, polymerase chain reaction (PCR) using fungal-specific primers helps identify fungi from FFPE tissues. Autopsy FFPE specimens have a disadvantage regarding the quality of DNA extracted compared with that of specimens obtained via biopsy or surgery. In the case of mucormycosis diagnosed postmortem histologically, we examined currently available molecular biological methods such as PCR, immunohistochemistry (IHC), and in situ hybridization (ISH) to identify fungi. It is reasonable that PCR with some modification is valuable for identifying fungi in autopsy FFPE specimens. However, PCR does not always correctly identify fungi in autopsy FFPE tissues, and other approaches such as ISH or IHC are worth considering for clarifying the broad classification (such as the genus- or species-level classification).
Insights
Identifying invasive fungal infections (IFIs) in hematopoietic stem cell transplant patients postmortem is challenging. Molecular methods like PCR, IHC, and ISH on formalin-fixed, paraffin-embedded (FFPE) tissues aid fungal identification from autopsy samples.
Area of Science:
- Medical Mycology
- Molecular Pathology
- Transplantation Medicine
Background:
- Invasive fungal infections (IFIs) are a significant cause of mortality in hematopoietic stem cell transplant (HSCT) recipients.
- Postmortem confirmation of IFIs often relies on formalin-fixed, paraffin-embedded (FFPE) tissues due to challenges with immediate sample acquisition.
- Accurate fungal identification is crucial for understanding disease progression and improving patient outcomes.
Purpose of the Study:
- To evaluate the utility of molecular diagnostic methods for identifying fungi in autopsy-derived FFPE specimens.
- To compare the effectiveness of polymerase chain reaction (PCR), immunohistochemistry (IHC), and in situ hybridization (ISH) for fungal detection and classification in postmortem tissues.
Main Methods:
- Histopathological examination of FFPE tissues.
- Molecular analysis using fungal-specific PCR primers on DNA extracted from FFPE samples.
- Application of IHC and ISH techniques for fungal identification and classification.
Main Results:
- PCR can identify fungi in autopsy FFPE specimens, but DNA quality can be a limitation.
- Histopathology combined with molecular methods offers improved diagnostic accuracy and reproducibility.
- While PCR is valuable, ISH and IHC are recommended for precise genus- or species-level fungal classification in challenging autopsy FFPE samples.
Conclusions:
- Modified PCR techniques show promise for fungal identification in autopsy FFPE tissues.
- A combination of diagnostic approaches, including PCR, IHC, and ISH, is essential for accurate fungal identification in postmortem settings.
- Further refinement of molecular techniques is needed to overcome limitations associated with DNA quality in FFPE samples for definitive fungal diagnosis.
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