Diagnosis of medullary thyroid microcarcinoma by calcitonin measurement in fine-needle aspiration washout

Ditescu Bogdan Radu; Luca Diana-Simina; Stan Andrei; Caragheorgheopol Andra; Terzea Dana; Alexandru Niculescu Dan; Poiană Cătălina

doi:10.1530/endoabs.99.P171

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Endocrine Abstracts (2024) 99 P171 | DOI: 10.1530/endoabs.99.P171

ECE2024 Poster Presentations Thyroid (58 abstracts)

Diagnosis of medullary thyroid microcarcinoma by calcitonin measurement in fine-needle aspiration washout

Bogdan Radu Ditescu ¹ , Luca Diana-Simina ¹ , Stan Andrei ¹ , Caragheorgheopol Andra ² , Terzea Dana ³ , Niculescu Dan Alexandru ^1,4 & Poiană Cătălina ^1,4

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¹Department of Pituitary and Neuroendocrine Disorders, C. I. Parhon National Institute of Endocrinology, Bucharest, Romania; ²Research Laboratory, C. I. Parhon National Institute of Endocrinology, Bucharest, Romania; ³Pathology Department, C. I. Parhon National Institute of Endocrinology, Bucharest, Romania; ⁴Department of Endocrinology, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania

Introduction: Medullary thyroid carcinoma (MTC) is an uncommon thyroid malignancy arising from calcitonin-producing parafollicular cells. Micro-MTC is defined traditionally as MTC that measures ≤1 cm and represents a very rare entity. Ultrasound-guided fine-needle aspiration biopsy cytology (FNAB-C) sensitivity is about 63% for MTC and can be improved by measurement of calcitonin in the needle washout (FNA-CT). The value of FNA-CT in micro-MTC has not been studied. Our aim was to further investigate the value of FNA-CT as a diagnostic marker for micro-MTC.

Methods: We retrospectively analyzed all patients with thyroid micronodules and elevated serum calcitonin in whom FNAB-C and FNA-CT was performed during 2019-2023. Clinical, imaging, biochemistry and pathology parameters were retrospectively extracted.

Results: A total of 21 patients with elevated serum calcitonin and thyroid micronodules detected on ultrasound, underwent FNAB-C and FNA-CT. Furthermore, 12 patients underwent surgical treament whenever a cytological suspicion for malignancy existed. Validation of the technique for these cases was realized through the correlation between the cytologic diagnosis of thyroid FNAB and the postoperative histopathologic diagnosis. The specificity and sensitivity for MTC was 100% for both FNAB-C and FNA-CT at a cut-off value of 62.7 pg/ml.

Conclusion: Early clinical detection and preoperative confirmation of MTC still represent a diagnostic challenge in clinical practice and through this study we demonstrated that FNA-CT measurement is an effective method for micro-MTC diagnosis. We set our own laboratory cut-off for calcitonin at 62.7 pg/ml. Although FNA-CT is a important complementary diagnostic tool, it should only be integrated but not substitute FNAB-C to detect micro-MTC.