Varicose veins of lower extremities represent a common medical condition with minimally invasive percutaneous endovenous ablation techniques as a treatment of choice. A very rare complication is a catheter migration in the deep venous system. In the literature only 7 cases have been published so far, with only 2 cases with migration to the systemic circulation and heart involvement. In this paper we present an interesting case report from the perspective of a thoracic surgeon with the finding of a laser ablation catheter remnant in the left pleural cavity during thoracoscopic exploration for a spontaneous hemothorax in a 47-year old male patient after collapse. A similar complication affecting the pleural cavity has not been published before. In this paper we discuss possible routes of the cathether migration into the left pleural cavity, impending complications when a part of the catheter is left behind in the body and the means of prevention of these serious potentially fatal complications even after many years following the initial treatment.