Abstract
BACKGROUND: Peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS), is a rare, aggressive subtype of non-Hodgkin lymphoma with no defining immunophenotypic or genetic signature. Extranodal involvement is common, but extensive infiltration without lymphadenopathy is rare. CASE SUMMARY: A 69-year-old man presented with progressive cardiomyopathy and conduction disease, without systemic symptoms or imaging evidence of malignancy. Workup revealed an atypical T-cell infiltrate on endomyocardial biopsy, but peripheral blood flow cytometry and imaging were unrevealing. Diagnosis remained uncertain during life. DISCUSSION: The patient rapidly deteriorated and died. Autopsy revealed diffuse T-cell infiltration in the heart, kidneys, and adrenal gland. Immunohistochemistry was suspicious for lymphoma. Despite biopsy findings, incomplete staging and lack of definitive clonal markers delayed diagnosis. Final diagnosis of PTCL-NOS was made. TAKE-HOME MESSAGES: This case presents cardiac-predominant PTCL-NOS with multiorgan infiltration and no lymphadenopathy. In cases of unexplained cardiomyopathy, endomyocardial biopsy is critical, and malignancy must be considered, even without systemic signs.