Effectiveness of surgery and chemotherapy with immune checkpoint inhibitor for cardiac metastatic squamous cell carcinoma of unknown primary.

We present a case of squamous cell carcinoma of unknown primary (SCCUP) with metastasis to the right ventricle (RV) successfully treated through surgical resection and postoperative chemotherapy with an immune checkpoint inhibitor (ICI). A 50-year-old woman presented with dyspnea, prompting transthoracic echocardiography that revealed a mobile, irregular RV mass measuring 40 × 32 mm. Contrast-enhanced computed tomography (CT) revealed masses in the RV and the right pulmonary artery, which was totally occluded. Emergency surgical resection of both masses was performed to avoid sudden death. Histopathological analysis confirmed squamous cell carcinoma; however, the primary origin of the masses remained unidentified despite extensive evaluations, including positron emission tomography-CT. The final diagnosis was SCCUP. Immunohistochemistry indicated positive programmed cell death ligand 1, and postoperative chemotherapy with an ICI was administered. One year post-surgery, the patient remains healthy with no sign of recurrence. Learning objective: This case shows the treatment of squamous cell carcinoma of unknown primary (SCCUP) with cardiac metastasis through emergency surgery and postoperative immunotherapy. Despite the poor prognosis associated with cardiac metastatic malignant tumors and the lack of established treatment guidelines, this case highlights the potential benefits of surgical intervention and the efficacy of immunotherapy in managing cardiac metastatic SCCUP, with the patient remaining with no recurrence one-year post-surgery.