RESUMO
INTRODUCTION: Secondary cardiac malignancies are much more common than primary cancers. Metastatic cancers to the heart from other solid organs are well known and carry a poor prognosis. CASE PRESENTATION: An 83-year-old Hispanic veteran presented with breathlessness, cough, and weight loss. Imaging studies showed extensive pericardial effusion and multiple pericardial/epicardial masses. Biopsy showed poorly differentiated metastatic carcinoma with no definitive origin, based on lab, imaging, and extensive immunohistochemistry (IHC) studies. Gene panel testing showed microsatellite stable status. Programmed cell death 1 ligand (PD-L1) IHC was 100% in the tumor cells. He was started on pembrolizumab and had a complete resolution of symptoms. Subsequent imaging studies showed improvement in the multiple pericardial/epicardial masses. DISCUSSION: Immune checkpoint inhibitor (ICI) therapy has changed the treatment landscape of many malignancies since the approval of the first ICI, ipilimumab, for melanoma in 2011. To the best of our knowledge, this is the first reported case of successful treatment by ICI therapy in undifferentiated metastatic carcinoma of an unknown primary source to the heart.