Endocrine Abstracts

Background: Medullary thyroid cancers (MTC) originate from parafollicular C cells and constitute 3-5% of all thyroid cancers. Calcitonin (CT) measurement is useful in the diagnosis of MTC. The sensitivity and specificity of CT are low in the measurement alone, and the sensitivity and specificity increase when used with pentagastrin and calcium stimulation tests. However, the difficulty of accessing pentagastrin, the uncertainty of the cut-off value in calcium stimulation tests, the differences in calcitonin assay and the costs complicate the use of serum CT and stimulation tests in the diagnosis. For this reason, guidelines do not offer opposing or supportive recommendations about the routine measurement of CT in patients with thyroid nodules. In this study, we aimed to investigate the contribution of CT washout of the nodule (WO) to routine CT measurement for MTC diagnosis.

Methods: In our clinic for the last three years, calcitonin values have been routinely measured in patients with nodular thyroid disease. CT-WO is performed for the nodules of patients whose calcitonin values are still above the laboratory cutoff levels in repeated measurements after excluding confounding factors. CT-WO was implemented after the thyroid fine-needle aspiration biopsy specimen was spread on a slide. The remaining material was washed with 1 mL of saline, and then the CT level was measured. In this study, the results of 33 patients who were operated on will be presented.

Results: Papillary thyroid cancer (PTC) was found in 12 (36.4%), MTC in 14 (42.4%) and benign pathology in 7 (21.2%) of the patients. CT washout was performed on 69 nodules of these patients before surgery. According to the pathology reports, eleven of these nodules were PTC, 13 were MTC, and 45 were benign. PTC and MTC were detected incidentally in two separate patients. In patients with MTC, serum CT and CT-WO values were significantly higher than the other two pathology groups (P=0.001). ROC analysis was performed for serum CT value, and the level 29.9 determined MTC with 100% sensitivity and 90% specificity (AUC=0.975 (0.932-1), P<0.001). Also, ROC analysis was performed for the CT-WO values of the nodules, and level 413.5 determined MTC with 100% sensitivity and 86% specificity (AUC=0.987 (0.965-1), P<0.001). The median MTC diameter in the thyroidectomy specimens was 1 cm (0.6-5.5). Micro MTC was detected in 8 (61.5%) of the patients.

Conclusion: CT-WO appears to be useful in diagnosing MTC early and accurately.