Cervicomediastinal magnetic resonance imaging in persistent or recurrent papillary thyroid carcinoma: Clinical use and limits

Cervicomediastinal magnetic resonance imaging (MRI) was evaluated in 13 con secutive persistent or recurrent papillary thyroid carcinoma (PTC) patients , previously treated by total thyroidectomy and radioiodine ablation. All h ad elevated thyroglobulin (Tg) levels and were therefore submitted to a new therapeutic radioiodine dose followed by a posttherapeutic whole-body scan (I-131-WBS),,and subsequent MRI. Patients with known distant metastases we re excluded from the study. Group 1 included 7 patients with a negative I-1 31-WBS, whereas cervical and/or mediastinal I-131-uptake was evidenced in t he other 6 patients (group 2). MRI was thus compared to I-131-WBS, and addi tionally in 8 reoperated cases, to histology. MRI was positive in 11 of 13 (85%) patients, corresponding to 23 of 55 (41.8%) histologically confirmed sites. In group 1, MRI was positive in 5 of 7 patients, with a sensitivity of 47% (15/32 histologically positive sites), allowing appropriate indicati on of surgery: 4 neck surgery, and 1 mediastinal dissection because of too distant lymph node foci. In group 2, MRI always showed more localization th an I-131-WBS; histology was obtained in 3. Because all the foci located in the mediastinal area (0.8 to 1.8 cm) were histologically confirmed (7/7 sit es), MRI avoided underestimation of surgery in the 8 reoperated patients. H owever, additional images were also observed corresponding to a normal thym us, a small neuroma or inflammatory lymph nodes, but pretracheal and very s mall nodes (less than 0.5 cm) were missed. In conclusion, although less spe cific than radioiodine scintigraphy, MRI can detect local persistent or rec urrent PTC, and seems particularly effective for evaluation of mediastinal involvement.