Calcitonin levels in washout of cytology needle on thyroid nodule without suspicion of medullary thyroid carcinoma

T. Martin; C. Garcia; N. Gonzalez; P. Sanchez; A. Barco; V. Martin; A. Sendon

Introduction: We study the calcitonin levels measurement in the washout of FNAB needles after sampling each thyroid nodule (FNAB-CT) as an approach to calcitonin normal value in them and distinguish of MTC and to correlate with serum CT (sCT) and cytology FNAB.

Material & Methods: 109 consecutive subjects (mean age 53.7±13.4, range 18–85 yr, 79.8% females, 27.5% smokers, 18.3% autoimmune thyroid disease) initially no suspicious for MTC who underwent FNAB for thyroid nodule served as study poblation (mean size 20.1±9.3 mm.) FNAB was performed in thyroid nodule and the same needle and syringe used for FNAB was washed with 1 mL of % 0.9 sodium chloride solution and sent to the laboratory for calcitonin evaluation (FNAB-CT). Both serum and washout calcitonin were measured by chemiluminescence assay (IMMULITE 2000)

Results: In patients with a thyroid nodule under evaluation, sCT were 3.07±3.22 ng/l (range 2–19.4 ng/l) and and FNAB-CT values 3.98±10.36 ng/l (range 2–97 ng/l), respectively. In 2 patients, FNAB-CT values were 10x higher than the highest values found, but cytology results were compatible with a benign thyroid lesion and papillary carcinoma; both were submitted to surgery found MTC (serum CT/FNAB-CT: 382/32.250 ng/ml, respectively) and microMTC/C-Cell hyperplasia (serum CT/FNAB-CT: 4.5/1.150 ng/ml, respectively) In the other cases FNAB-CT values not show significative correlation with any study parameters (age, sex, autoimmune thyroiditis, tobacco, BMI) except weakly with sCT (r: 0.17, P<0.04).

Conclusion: Assaying calcitonin (CT) in the wash-out fluid from fine-needle aspiration biopsies (FNAB.CT) can be an additional and precocious approach to diagnosis of MTC

Values are expressed as mean±DE and range. sCT (serum calcitonin) nCT (calcitonin in thyroid nodule FNAB-washout)

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

**Table 1** Levels of sCT & nCT in relation to ecographic and cytological diagnostics
DIAGNOSTICS	sCT	nCT
Thyroid single nodule (n=39)	2.49±1.33 (2–8.1)	6.36±16.3 (2–97)
Multinodular Goitre (n=42)	3.79±4.6 (2–19.4)	2.02±0.02 ( 2–2.1)
Cystic lesion (n=11)	4.48±5.26 (2–19.4)	≤2
Autoimmune Disease (n=16)	2.6±1.15 (2–6.5)	3.59±1.15 (2–13.2)
Follicular neoplasm (n=4)	2.27±0.55 (2–3.10)	3.95±3.0 (2–8.4)
Papillary Cancer (n=4)	≤2	≤2
Material hematic (n=5)	2.6±1.34 (2–5)	2.31±0.77 (2–3.9)

Endocrine Abstracts

P1815