Primary tumors of the heart are rare, whereas cardiac metastases, most frequently from adenocarcinomas, occur in up to 20% of malignant tumors. We report about a 61-year-old female patient who was admitted with recurrent stress-induced dizziness, intermittent tachycardia and a fall due to a pre-syncope. Echocardiography showed a left atrial tumor with the typical features of a pediculated myxoma, leading to open heart surgery. However, histopathology revealed a 2.2 x 1.5 cm adenocarcinoma. The subsequent search for a primary tumor, including tumor markers and (18)F-FDG-PET, was unsuccessful, as was a second thorough diagnostic workup half a year later. The tumor was therefore classified as a primary cardiac adenocarcinoma.