We report the case of an 81-year-old man with sudden incomplete left hemianopsia. Brain computed tomography (CT) showed a right occipital hypodensity which did not seem related to the consequences of embolic stroke as atrial fibrillation consequence (the patients suffered from permanent atrial fibrillation, CHA2DS2-VASc score=5, but rather showed the characteristics of ischemic lesion due to other causes. Therefore, diagnostic work up was performed and revealed advanced non-small cell lung cancer invading left atrium through upper pulmonary veins. No others secondary lesions were detected. Cardiac involvement in cancer is an unusual finding in clinical practice and rarely stroke is the first manifestation. There are no reported cases of neoplastic embolism to the brain from cancer in the left atrium whose origin is into the lung. The patient started palliative chemotherapy. This report highlights the need for a holistic approach in medicine as the obvious diagnosis could not be the right one.