Objective: The aim of the study was to evaluate the usefulness of calcitonin (CT) assay in fine-needle aspiration biopsy (FNAB) washout fluid alone or combined with cytology in the presurgical study of medullary thyroid carcinoma (MTC) patients with thyroid nodules (TNs) and of suspicious neck MTC recurrences/metastases. Subjects and Methods:A total of 36 ultrasound-guided FNABs were performed in neck masses from 23 patients with borderline or high basal and pentagastrin-stimulated serum CT. Cytology and CT-FNAB were performed on a total of 18 TNs and three neck lymph nodes (LNs) from 12 patients examined before thyroidectomy, and on six suspicious local recurrences (LRs) and nine LNs from nine totally thyroidectomized MTC patients. On the basis of CT-FNAB values found in 15 non-MTC lesions, CT-FNAB more than 36 pg/ml was considered as indicative of MTC.Results: All 21 positive CT-FNAB lesions (10 TNs, six LNs, and five LRs), 13 with positive cytology, were confirmed as MTC at histology. Of the 15 negative CT-FNAB suspicious masses (eight TNs, six LNs, and one LR), five displayed a benign lesion at histology. The remaining 10 cases, all with benign cytology, were not operated on, and no evidence of MTC was detected at follow-up. CT-FNAB reached 100% sensitivity and specificity for MTC, while cytology displayed 61.9% sensitivity and 80% specificity. calcitonin (CT) has been proposed as a routine assay in the diagnostic evaluation of all thyroid nodules (TNs) for early detection of medullary thyroid carcinoma (MTC) (1-4). Fine-needle aspiration cytology represents the main tool in the diagnostic evaluation of TNs, but it is not frequently proposed as a routine procedure in patients with high-serum CT, due to its low sensitivity and specificity (1, 5). Neck ultrasound (US) with color flow Doppler sonography (CFDS) and US-guided fine-needle aspiration cytology is the current diagnostic approach for the identification of MTC neck lymph node (LN) metastases both before and after thyroidectomy (6 -8). A similar approach is used to identify neck recurrences/metastases of differentiated follicular and papillary thyroid carcinoma, where the assay of thyroglobulin (Tg) in fine-needle aspiration biopsy (FNAB) wash-out fluid (Tg-FNAB) represents an additional highly reliable marker (9 -11). When compared with Tg-FNAB, no study has been performed to evaluate the usefulness of CT assay in FNAB (CT-FNAB) fluid alone or combined with cytology. ConclusionsThe aim of this study was to assess the clinical usefulness of CT-FNAB in the identification of primary MTC and its neck LN metastases or recurrences. From 2003From -2006 US-guided FNABs were performed in 23 patients with high-serum CT. These included 21 lesions (18 TNs and three neck LNs) from 14 patients before thyroidectomy and 15 neck masses (six suspicious local recurrences and nine neck LNs) from nine patients after total thyroidectomy for MTC. Patients and Methods Patients studiedAll patients (13 women, age range 36 -76 yr, and 10 men, age range 25-69 yr) were submitted ...