The usefulness of calcitonin assay in fine needle aspiration biopsy (FNAB) fluid of neck masses of patients with primitive and metastatic medullary thyroid carcinoma.

OBJECTIVE: To evaluate the usefulness of calcitonin (CT) assay in FNAB wash-out fluid (CT-FNAB) alone or combined to cytology in the pre-surgical study of MTC patients with multinodular goiter (MNG) and of suspicious neck MTC recurrences/metastases. PATIENTS AND METHODS: Thirthy-six ultrasound (US)-guided FNAB were performed in neck masses from 23 patients with borderline or high basal and pentagastrin (PG) stimulated serum CT. A total of 18 nodules and 3 neck lymph nodes (these latter present in the same subject) were from 12 MNG patients and 15 suspiciuos neck masses (6 local recurrences and 9 neck lymph nodes) were from 9 totally thyroidectomized MTC patients. Conventional cytology and CT-FNAB were always associated to PG stimulating test. On the basis of CT-FNAB values found in 15 non-MTC lesions, CT-FNAB>24 pg/ml (twice of the highest observed value) was considered as indicative of MTC. Thyroid 99mTc-pertechnetate scintiscan were also performed in patients with MNG. RESULTS: As displayed in the Table, all the 21 positive CT-FNAB neck lesions (10 nodules, 6 neck lymph nodes and 5 local recurrences), 13/21 with positive cytology, were confirmed as MTC at histology. Among the 15 negative CT-FNAB neck masses (8 nodules, 6 suspicious neck lymph nodes and 1 suspicious local recurrences) 5 underwent to surgery and a benign lesion was confirmed at histology. The remaining 10 cases (all with benign cytology) were not operated and no evidence of MTC has been detected so far at follow-up of 2.5 years. CT-FNAB+ n= 21 CT-FNAB– n= 15 Cyto+ n=13 Cyto- n=8 Cyto+ n=1 Cyto- n=14 Histo+ n=13 Histo+ n=8 Histo- n=1 Histo- n=4* * 10 lesions not operated displayed benign clinical features at follow-up Taken together, CT-FNAB reached 100% of sensitivity and specificity for MTC, while cytology displayed only 61.9% of sensitivity and 93.3% of specificity. CONCLUSIONS: US-guided CT-FNAB provided to be a very useful tool to localize primitive MTC in MNG patients and recurrences or lymph node metastases in MTC operated subjects, with much more sensitivity and specificity than cytology. This may have important implications in planning the adequate surgical approach.