Endocrine Abstracts

Background

Medullary thyroid carcinoma (MTC) accounts for 3–5% of thyroid cancers, but recurrent MTC, manifested by elevated calcitonin levels, is a common problem. We aimed to perform a calcitonin washout procedure simultaneously with cytological evaluation and compare their effectiveness to diagnose metastatic lymph nodes.

Methods

94 patients diagnosed with MTC were recruited from our institutional database from 2010–2021. The analysis of calcitonin washout procedure (CTW) and fine-needle aspiration (FNA) cytology for metastatic lymph nodes were recorded for recurrent MTC. Only one cytologist performed the cytological examination. The cut-off level above ≥100 pg/ml was determined as a pathologic lymph node. The demographic features, mean age at diagnosis, laboratory analysis of preoperative and postoperative calcitonin and Carcinoembryonic antigen (CEA), cytopathological data were all collected.

Results

The median age at diagnosis was 40.7 ± 17 years; the mean CTW level was 1800 (142–9000) pg/ml, the mean preoperative CT level was 620 (54–9000) pg/ml, and the mean CEA level was 9.4 (0.5–1958). Out of 94 patients, 32 were recurrent cases. CTW and FNA procedures were applied for 44 suspicious lymph nodes. 43 cytological examination were done for these lymph nodes. The FNA results’ distribution was 4.6% reactive lymph node(n:2), 11.6% non-diagnostic(n:5), 81.3% (n:35) MTC and 2.32% (n:1) suspicious for malignancy. The two reactive lymph node cytology had CTW levels of 800 pg/ml and 2942 pg/ml, so they were operated on and diagnosed as MTC. 44 positive CTW procedures were applied, and 42 of them were compatible with MTC. The false positive lymph nodes were; a reactive lymph node with a CTW result of 221 pg/ml and a cytologically non-diagnostic lymph node with a CTW result of 800 pg/ml.

Conclusion

Recurrent MTC is a progressive disease in half of the cases, but it can be handled with correct diagnostic methods and surgery. CTW procedure is an easy and quick laboratory test as compared with cytological evaluation. According to our results, CTW measurements were also more accurate than cytological examination when defining pathological lymph nodes. CTW evaluation was mainly evaluated for either thyroid nodules alone or combined with neck lymph nodes. This is the first and largest study evaluating the metastatic lymph nodes of MTC with CTW and cytology together.