Needle tract seeding of thyroid cancer after biopsy of distant metastasis: a retrospective cohort.

Imaging-guided percutaneous core needle biopsy is currently the most common technique for the investigation of potentially malignant bone lesions. It allows precise needle placement and better visual guidance, leading to improved diagnostic accuracy. Needle tract seeding (NTS) is a rare complication of biopsies in general, and its true incidence remains unknown. This study aimed to assess the risk of NTS in patients with thyroid cancer who underwent bone biopsy. For our cohort, we extracted data from the electronic medical record at the Mayo Clinic in Rochester (Minnesota, USA). Inclusion criteria included patients with a history of thyroid cancer who underwent biopsy for bone metastasis between 1/1/2014 and 10/1/2023. We identified a cohort of 20 patients that fit our inclusion criteria. Of these 20 patients, 2 patients developed NTS after CT-guided bone biopsy. Cases of seeding had a larger tumor size, a more aggressive histopathological presentation, a significantly shorter duration between cancer diagnosis and bone metastasis, and underwent more tumor manipulation procedures, such as biopsy and radiofrequency ablation, in contrast to those without seeding. In conclusion, our study identified NTS to have an incidence of 10% after biopsies of bone metastasis related to thyroid carcinoma. These are likely the result of an interplay of risk factors, including tumor biology, penetrated tissues and procedural technical details. Further studies with larger sample sizes are needed to confirm our findings and identify strategies to mitigate NTS.