Endocrine Abstracts

DTC carries a good prognosis when adequately treated by means of total thyroidectomy, iodine-131 (I-131) treatment and TSH-suppressive therapy, and carefully followed up (i.e. serum thyroglobulin, I-131 total). In some cases, however, false-positive scans can occur. A 42-yr-old woman with recurrent chest infections and bronchiectasis was submitted to total thyroidectomy because of a13 mm nodule in the right lobe that showed a papillary thyroid carcinoma at FNAB histological examination. The patient was then submitted to I-131 treatment with 3700 MBq after L-thyroxine withdrawal. The post therapeutic dose total body scan showed a residual iodine uptake in the thyroid bed attributable to thyroid remnant, compatible with the thyroglobulin serum level (tg=6.49 ng/ml), and a low bilateral uptake in the lung fields. A I-131 total body scan (185 MBq) following recombinant (rh)-TSH administration four months after the therapeutic dose of radioiodine showed a marked and diffuse uptake in the lungs with tg levels below the detection levels. A CT of the chest confirmed the bronchiectasis appearance of the bronchial tree. No further therapeutic dose of radioiodine was administered and the patient was followed up with periodic serum tg level determination during TSH suppressive treatment and neck echographic evaluation. Two years later, another I-131 scan (rh-TSH) showed the same picture of diffuse uptake of radioiodine in the lungs, with undetectable stimulated serum tg, while CT of the chest confirmed the presence of bronchiectasies with no other lesions referable to metastatic involvement of the lungs. This case claim attention about the possible false-positive results of I-131 scan in DTC follow up in patients affected by infective and inflammatory diseases of the lungs, emphasizing the importance of interpreting the I-131 uptake on the bases of clinical context, imaging and laboratory findings (serum tg). Recognition of false-positive cases permit to avoid further radioiodine therapeutic doses administrations that are not indicated and potentially associated by side-effects (sialadenitis, gastritis, other malignancies, and pulmonary disease with lung fibrosis). and that can cause an emotional trauma for the patient, often leading to legal controversies.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector