Rationale: Correct catheter tip placement is the foundation for catheter utilization and the prevention of catheter-related complications. We describe 2 unusual peripherally inserted central catheter (PICC) malpositions in the left thymic vein and the right middle thyroid vein, which are, to our knowledge, the first 2 cases of PICC malposition in these 2 veins.

Patient concerns: Both patients had subtle clinical signs of catheter malposition on initial post-procedure chest X-ray radiography or during catheter duration. However, all signs were overlooked.

Diagnoses: Two catheter malpositions were incidentally discerned and diagnosed using a winding and delayed modality.

Interventions: One of the catheters was removed at a local hospital, the other catheter tip was adjusted to the superior vena cava by the advanced practice nurse.

Outcomes: Two catheter malpositions were incidentally discerned and diagnosed over the course of a winding and delayed procedure, resulting in belated catheter manipulation.

Lessons: Although neither patient experienced significant catheter tip-related events, the delayed diagnostic process led to the presentation of these 2 unusual cases, to guide further recognition of this complication. Some principles should be followed to avoid rare PICC malposition and its fatal complications, including verification of tip before using catheter, use of real-time imaging guidance, regular monitoring of long-term dwelling catheter, and proactive assessment of catheter or direct communication with radiologists particularly in cases where catheter tip malposition is highly suspected.

Li X, Liu C, Chen H, Wu Z, Liang D, Zhang X. Unusual malposition of peripherally inserted central catheters into the thymic vein and middle thyroid vein: A case series. Medicine (Baltimore). 2025 Jun 20;104(25):e42800. doi: 10.1097/MD.0000000000042800. PMID: 40550102.