Malignant pericardial effusion is common, being reported in 5–15% of all cancer patients. It most commonly arises from metastasis of lymphomas and of tumours of the lung, breast and, infrequently, the gastrointestinal tract. We describe the case of a 76-year-old woman who presented to the emergency room with cervical adenopathies and clinical signs of acute heart failure. The nodes were biopsied and found to be consistent with adenocarcinoma of the colon. CT showed thoracic lymphatic involvement but no evidence of other organ involvement. The patient developed cardiac tamponade and required emergent pericardiocentesis. To our knowledge, this is the first report of metastatic colon cancer without direct involvement of the pericardium or other solid organs. LEARNING POINTS Large pericardial effusions are common in cancer patients. The pericardium in cancer patients may be affected by haematogenous or lymphatic spread or by local extension. A gastrointestinal origin of malignant pericardial effusions is rare but should be considered as a possible diagnosis. Keywords: Colon, cancer, metastasis, cardiac tamponade INTRODUCTION Malignant pericardial effusion occurs in some cancer patients[1] and commonly arises from metastatic disease[2]. Colon cancer is a common form of cancer[3] and 20% of patients already have metastatic disease at the time of diagnosis[3]. Colon cancer typically metastasizes to the regional lymph nodes, liver, lung and peritoneum[4]. Pericardial effusion is a common entity often overlooked in clinical practice. In developed countries, the aetiology remains undetermined in 50% of patients and is attributable to cancer in up to 25% of cases. In contrast, in developing countries, infections such as tuberculosis are the main causes of pericardial effusion (>60%)[5].