Background: lymphomas arising in cardiac myxomas represent a particularly rare pathology, with only few cases reported in the literature. Case presentation: we report a completely exeresis of malignant lymphoma arising in a cardiac myxoma in a 44 years-old female patient. The myxoma presented like a floating mass within the left atrium with a maximum diameter of 3.5 cm. The clinical post-operative period was uneventful and the patient was dismissed on sixth post-operative day. Conclusions: This case reinforces the concept of a radical exeresis of cardiac neoplasms