FNA in medullary thyroid carcinoma

TOPIC: Hormone determinations in wash-out fluid from FNA

Title: Calcitonin measurement in wash-out fluid from fine needle aspiration of neck masses in patients with primary and metastatic medullary thyroid carcinoma.

Authors: Boi F, Maurelli I, Pinna G, Atzeni F, Piga M, Lai ML, & Mariotti S.

Reference: Journal of Clinical Endocrinology & Metabolism 92: 2115-2118, 2007

Summary

Objective

The aim of the study was to evaluate the usefulness of calcitonin (CT) assay in fine-needle aspiration biopsy (FNAB) wash-out 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 & 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 3 neck lymph nodes (LNs) from 12 patients examined before thyroidectomy, and on 6 suspicious local recurrences (LRs) and 9 LNs from 9 totally thyroidectomized MTC patients. On the basis of CT-FNAB values found in 15 non-MTC lesions, CT-FNAB values more than 36 pg/ml were considered as indicative of MTC.

Results

All 21 positive CT-FNAB lesions (10 TNs, 6 LNS, & 5 LRs), 13 with positive cytology, were confirmed as MTC at histology. Of the 15 negative CT-FNAB suspicious masses (8 TNs, 6 LNs, & 1 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 during follow-up. CT-FNAB reached 100% sensitivity and specificity for MTC, while cytology displayed 61.9% sensitivity and 80% specificity.

Conclusions

Ultrasound-guided CT-FNAB was the best tool to identify primary MTC and LRs/node metastases in MTC operated patients. This may have important implications in the management of MTC.

Commentary

Two recent studies of medullary thyroid carcinoma (MTC) extend the technique reported by Pacini et al. in 1992, who showed that the assay of thyroglobulin in the needle/syringe wash-out from fine needle aspiration biopsy (FNAB) of neck lymph nodes could be definitive in demonstrating that neck lymph nodes were metastases from differentiated thyroid carcinoma (Pacini et al., JCEM 74:1401, 1992). This hormone assay application has also been validated for parathyroid hormone (Kiblut et al., World J Surg 28:1143, 2004; Maser et al., Ann Surg Oncol 13:1690, 2006). More recently, it was also shown that the assay of calcitonin (CT) can provide crucial information from ultrasound/FNAB studies (Present article, and Kudo et al., Thyroid 17:635, 2007).

In the present article, Boi et al. reported 21 studies that were positive for CT on fine needle wash-out assays, with a better sensitivity & specificity than was obtained from cytology. Kudo et al. reported 5 thyroid nodules positive for medullary carcinoma, with only one of which identified by cytology. CT assay values in the needle wash-out were 300 to 10.000-fold higher than in other thyroid abnormalities that were biopsied.

In this technique, the equipment used for FNAB is washed out with 1 ml of assay diluent after preparation of routine cytological samples. Precisely targeted surgery may be facilitated by answers to the following questions: 1. Does a newly recognized neck lymph node contain metastatic thyroid tissue? 2. Does a mass of doubtful significance, seen on ultrasound in differentiated thyroid cancer or medullary carcinoma follow-up, contain metastatic or recurrent tissue? 3. Is a lump seen on ultrasound a parathyroid adenoma (if a rapid assay is available, the technique may also be useful intra-operatively)? 4. Is a thyroid nodule, lymph node or tissue mass, a focus of medullary thyroid carcinoma?

The results are qualitative, but masses that are hormone-positive give results orders of magnitude higher than serum concentrations or hormone-negative lesions. To date, no false-negative results due to -hook effects- have been reported, but this important possibility could be addressed by assaying samples in dilution (Lebouef et al., JCEM 91:361, 2006). Summary and commentary prepared by Jim Stockigt (related to Chapters 6(d), 18, & 21 of TDM)