Suspected track-site seeding as an isolated deep SH-SCM papillary thyroid carcinoma lesion years after TOETVA

Papillary thyroid carcinoma (PTC) has an excellent prognosis, and the transoral endoscopic thyroidectomy vestibular approach (TOETVA) is increasingly used in selected low-risk patients. However, creation of long working tunnels may predispose to tract-related tumor seeding, and deep tract recurrences have rarely been reported.

A 29-year-old woman underwent right hemithyroidectomy with central neck dissection via TOETVA in 2016 for a 3 cm encapsulated PTC with one metastatic central node. Serial ultrasounds over five years showed no disease before a three-year lapse in follow-up. In 2024, ultrasound detected a new 1.1 cm hypoechoic nodule anterior to the left sternohyoid; by late 2025, it had enlarged to about 2 cm and cytology confirmed PTC. Computed tomography demonstrated an enhancing mass in the deep left sternohyoid-sternocleidomastoid (SH-SCM) intermuscular compartment, noncontiguous with the thyroid bed and outside usual nodal chains. The lesion was excised en bloc via a supraclavicular approach, and histology again showed PTC without lymph node architecture. Review of the index TOETVA video revealed deviation of the vestibular tunnel into the SH-SCM space, where dissected central nodal tissue, including the metastatic node, had been temporarily placed.

This isolated PTC recurrence in the deep SH-SCM plane, detected about eight years after TOETVA, is highly suggestive of delayed tract-related implantation with a latency of at least five years, although causality cannot be proved. The case emphasizes strict adherence to recommended dissection planes, careful handling of lymph node specimens, and consideration of extended, access-tract-oriented ultrasound surveillance in young patients undergoing TOETVA.