We report a case of a cancer patient who displayed a persistent left superior vena cava (PLSVC) after implantation of a central venous catheter (Port-a-Cath), as revealed by angiography. This anomaly is rather rare (0.3% of healthy individuals), and the few studies on the long-term maintenance of an implant in situ are not very informative. Nevertheless, based on the acceptable venous caliber and the patient's serious clinical situation, we decided to leave the catheter in place and perform infusional chemotherapy and supportive therapy with careful and continuous control. The patient died after 8 months of this therapy. No complications attributable to the catheter were observed. We think that the risk is acceptable in similar conditions.