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As an adjunct to cytologic examination of fine-needle aspiration specimens in athyrotic individuals treated for medullary thyroid carcinoma to confirm or exclude metastases in enlarged or ultrasonographically suspicious lymph nodes
Calcitonin is a polypeptide hormone secreted by the parafollicular cells (also referred to as calcitonin cells or C-cells) of the thyroid gland. Malignant tumors arising from thyroid C-cells (medullary thyroid carcinoma: MTC) usually produce elevated levels of calcitonin. MTC is an uncommon malignant thyroid tumor, comprising <5% of all thyroid malignancies. Measurement of serum calcitonin is used in the follow-up of patients who underwent surgical removal of the thyroid gland.
Studies have reported that the measurement of calcitonin in fine-needle aspiration biopsy (FNAB)-needle washes improves the evaluation of suspicious lymph nodes in patients with a history of MTC when used in combination with cytology. Comparing the results of calcitonin in the needle rinse with serum calcitonin is highly recommended. An elevated calcitonin in the serum could falsely elevate calcitonin in the washings, if the rinse is contaminated with blood. In these cases only calcitonin values significantly higher than the serum should be considered as true-positives.
Cytologic examination and measurement of calcitonin can be performed on the same specimen. To measure calcitonin, the FNA needle is rinsed with a small volume of normal saline solution immediately after a specimen for cytological examination (for a smear or CytoTrap preparation) has been expelled from the needle. Calcitonin levels are measured in the needle wash.
An interpretive report will be provided.
In athyrotic patients with a history of medullary thyroid carcinoma (MTC), a fine-needle aspiration calcitonin value > or =5.0 pg/mL is suggestive of the presence of metastatic MTC in the biopsied lymph node.
Blood contamination during the biopsy might lead to false elevations of calcitonin in the fine-needle aspiration biopsy washout if serum calcitonin is significantly elevated. If blood was present in the washout, only calcitonin values significantly higher than the serum should be considered as true positives.
Immunometric assays can, in rare occasions, be subject to interferences such as "hooking" at very high analyte concentrations (false-low results) and heterophilic antibody interference (false-high results). If the clinical picture does not fit the laboratory result, these possibilities should be considered.
Results are dependent on accurate sampling and a maximum needle wash volume of < or =1.5 mL.
While the needle washes from several distinct needle passes or aspirations from a single area should be pooled, biopsies from different areas should be submitted as separate specimens.
Eighty-one lymph node washings were analyzed for calcitonin and thyroglobulin (as an indicator of the presence of metastatic thyroid tissue). All lymph node washings had a calcitonin value <5.0 pg/mL. A retrospective analysis of calcitonin (CATN) fine-needle aspiration (FNA) washings ordered clinically between 2008 and 2011 was performed. There were 65 samples in which the source was identified as lymph node. Calcitonin was undetectable (<5.0 pg/mL) in 57% of cases and >30 pg/mL in 37% of cases. In 6% of cases CATN was between 5 and 30 pg/mL.
1. Trimboli P, Rossi F, Baldelli R, et al: Measuring calcitonin in washout of the needle in patients undergoing fine needle aspiration with suspicious medullary thyroid cancer. Diagn Cytopathol 2012 May;40(5):394-398
2. Boi F, Maurelli I, Pinna G, et al: Calcitonin measurement in wash-out fluid from fine needle aspiration of neck masses in patients with primary and metastatic medullary thyroid carcinoma. J Clin Endocrinol Metab 2007 Jun;92(6):2115-2118
3. Kudo T, Miyauchi A, Ito Y, et al: Diagnosis of medullary thyroid carcinoma by calcitonin measurement in fine-needle aspiration biopsy specimens. Thyroid 2007 Jul;17(7):635-638