Late Onset of Cardiac Metastasis of a Melanoma following Nivolumab Immunotherapy

In this report, we present a case of cardiac metastasis of a malignant melanoma originating from the nasal cavity and presenting with cardiac tamponade detected during immunotherapy. The patient was a 66-year-old man diagnosed with malignant melanoma of the right nasal cavity 4 years ago. Two years ago, the size of the melanoma increased making it unresectable; therefore, he was treated thrice with a combination therapy of nivolumab and ipilimumab. Subsequently, the treatment was changed to single-agent nivolumab therapy, which was continuously administered for one and a half years. Imaging evaluation conducted every 3 months showed no distant metastasis. General malaise occurred, and the patient visited our department. He was diagnosed to have cardiac tamponade using echocardiography and was admitted to the emergency department of our hospital. He underwent pericardiocentesis. Computed tomography revealed an irregular mass extending from the right atrium to the inferior vena cava, and malignant melanoma metastasis was diagnosed through catheter biopsy and histology. As the tumor was unresectable, radiotherapy (30 Gy/10 fractions) and dacarbazine administration were performed on the right atrial mass, and pericardial effusion improved.