Catheter-related right internal jugular vein large thrombus formation after inadvertently malposition in the cranial direction Abstract Placement of a central venous catheter (CVC) is a routine procedure in major surgery and intensive care unit, acute severe complications associated with CVC-lead large thrombosis is rare. Current protocols and recommendations for clinical practice are not including tip confirmation in the right atrium and postprocedural scanning for complications. The tip position carries the risk of migration and thrombosis, customarily used ultrasound is less suitable for identifying the superior vena cava and right atrium. Not routinely widespread utilized and real-time employed method for ensure the correct position of the catheter tip in current in the perioperative period. We report a rare case of an inadvertently malposition of a catheter using ultrasound in the right internal jugular vein, the catheter tip went in the cranial direction at an acute angle. The misplacement caused severe discomfort and a large thrombosis of right internal jugular vein. We also show that a large CVC-related thrombosis formation treatment, CVC is kept under close surveillance, recovered satisfactorily and possibly avoid thrombus embolization in cancer patients guided by ultrasound. It needs to be vigilant for ultrasound assessment and surveillance in the perioperative period in cancer patients with indwelling CVCs in operating room.