A Tale of Two Myocarditides: Giant Cell Myocarditis and Sarcoidosis—A Pathologist’s Review

GCM is characterized by a fulminant clinical course, diffuse myocardial necrosis with multinucleated giant cells and eosinophilic infiltrate, and a predominantly CD8+ T-cell response. In contrast, CS typically presents with more indolent cardiac symptoms, well-formed nonnecrotizing granulomas with Langhans-type giant cells, and a CD4+ T-cell predominant response. GCM and CS share overlapping clinical and imaging features, and sometimes have histopathologic similarities as well. Emerging molecular data suggest transcriptional differences, but a subset of cases exhibit mixed or intermediate features, suggesting a possible disease spectrum. Advances in molecular profiling, standardized diagnostic criteria, noninvasive imaging modalities, and targeted immunosuppression may help refine diagnosis and treatment. Clarifying whether these conditions lie along a shared pathobiologic continuum remains an important goal for future research.