A Rapid Pathological Diagnosis Based on Unfixed Frozen Tissue Section Leads to the Misdiagnosis of Eosinophilic Myocarditis as Lymphocytic Myocarditis.
Saya Hirata, Kenichiro Suwa, Atsushi Sakamoto et al.
✦ AI-curated · Sources linked
Case in brief
A 64-year-old man presented with fever and progressive dyspnea, with clinical and imaging findings suggesting acute myocarditis. Rapid examination of unfixed frozen tissue from an endomyocardial biopsy indicated lymphocytic myocarditis. Subsequent assessment of formalin-fixed, paraffin-embedded tissue showed extensive eosinophilic infiltration, establishing eosinophilic myocarditis instead. Clinical and functional improvement followed immunosuppressive therapy.
What made this case unusual
The initial frozen-section interpretation differed from the diagnosis on formalin-fixed, paraffin-embedded tissue, where extensive eosinophilic infiltration was identified.
Diagnostic / clinical pearl
In suspected myocarditis, a rapid frozen-section result may not reflect the inflammatory pattern seen in formalin-fixed tissue; interpret it with awareness of the limitations of tissue preservation and processing.