ArticlesApplication of an immunodiagnostic method for improving preoperative diagnosis of nodular thyroid lesions
Introduction
Fine-needle aspiration cytology is well established in the primary diagnosis of benign and malignant thyroid disorders.1, 2, 3 However, there is general agreement that this procedure has some inherent limitations related to inadequate sampling and overlapping cytological features between benign and malignant follicular lesions4, 5, 6, 7, 8.” The morphological distinction of hyperplastic adenomatous nodules, well-differentiated follicular carcinomas, and follicular variants of papillary carcinoma is difficult, even for cytologists with extensive experience of thyroid fine-needle aspiration7, 8, 9.” Because specific criteria are required for the diagnosis of follicular carcinoma, particularly the unequivocal demonstration of capsular penetration and vascular invasion, well-differentiated follicular malignant lesions can also be difficult to distinguish from adenomas by histology.9, 10, This is the reason why cytology reports are commonly worded “probable benign follicular nodule” or “follicular nodule not otherwise specified”. As a consequence, the majority of patients with these lesions are referred for surgery. The psychological and social cost of this clinical approach is high for the patients, as well as for the health-care system, especially since less than 10% of the resected lesions will be definitively classified as carcinomas.2, 9, 10
Attempts to improve the preoperative diagnosis of thyroid nodules by use of strict instructions for obtaining adequate specimens and inclusion of clinical characteristics (such as sex, dimension of the nodule, character of the gland by palpation) have been reported.11, 12, 13 To date, however, even with optimum cytological preparation, no clinical, radiological, or laboratory test is sensitive and specific enough to distinguish reliably whether a follicular lesion identified by fine-needle aspiration is benign or malignant.
If reliable markers for detecting malignant thyrocytes are available, accurate preoperative diagnosis of thyroid cancer and appropriate clinical treatment should be possible. Several molecules have been identified by immunochemistry and reverse-transcriptase PCR as potential targets for immunocytodiagnosis of thyroid malignant disease. Among these, CD44v6 and galectin-3 seem to be promising.14, 15, 16, 17 CD44 is a polymorphic family of immunologically related cell-surface glycoproteins, which have a functional role in regulating several physiological and pathophysiological processes, including cell-cell and cell-matrix interactions, cell migration, and tumour growth and progression.15, 18 CD44 can be expressed on the cell surface as a standard receptor (CD44s, the putative receptor for hyaluronic acid), as well as multiple isoforms (CD44v), the expression of which is qualitatively and quantitatively altered during tumour growth and progression.15, 18, 19, 20 Interestingly, under normal conditions, only CD44s is expressed on the cell surface of non-proliferating thyrocytes. 14, 15, 16, 17 By contrast, previous studies showed at molecular14, 21 and protein level14, 22, 23, 24, 25 that expression of the [β-galactosil-binding protein galectin-3, which is also involved in regulating cell-cell and cell-matrix interactions, is restricted to malignant transformed thyroid cells. This study aimed to assess, in a large multicentre analysis, the clinical usefulness of a novel and promising immunocytomorphological approach to the preoperative characterisation of thyroid nodules.
Section snippets
Monoclonal antibodies and immunochemical assay
An extensive immunophenotypical analysis was done on 1009 thyroid lesions, comprising well-characterised formalin-fixed and paraffin-embedded tissue specimens (618 cases) and cell-blocks (165 cases) from selected benign and malignant lesions (retrospective analysis), as well as fresh cytological samples (226 cases) obtained preoperatively by ultrasound-guided fine-needle aspiration, from patients with palpable thyroid nodules, candidates for surgical resection (prospective study).
Monoclonal
Retrospective analysis of thyroid samples
618 samples of thyroid tissue taken from patients who had undergone surgical resection of the thyroid gland for benign or malignant lesions were tested for galectin-3 and CD44v6 expression (table 1).
In 75 cases of normal thyroid tissues, neither CD44v6 nor galectin-3 molecules were expressed. Among 287 histologically defined benign thyroid tissue samples, comprising different forms of thyroiditis, nodular hyperplasias, adenomas, and the normal cases, 280 did not express galectin-3, whereas
Discussion
An estimated 4% of people in the USA between the ages of 30 and 60 years have one or more palpable thyroid nodules. Most of these lesions are benign, so the indication for their surgical removal should be as narrow as possible.8, 9 Although the majority of papillary carcinomas and most forms of thyroiditis are easily detected by fine-needle aspiration cytology, preoperative discrimination between benign and malignant follicular lesions is still very difficult.8, 9, 10, 11, 12, 13 In this study,
Thyroid Cancer Study Group: Other Coauthors
Rino Belloco (Department of Medical Epidmiology, Karolinska Institute, Stockholm, Sweden); Marco Paolo Martegani, Fabrizio Del Prete, Pier Giorgio Natali, Anna Tofani (Laboratory of Immunology and Nuclear Medicine, Regina Elena Cancer Institute, Rome, Italy); Enrico Saggiorato (Department of Biological and Clinical Sciences, University of Turin, Turin, Italy); Antonella Marzullo, Tiziana Pisani (Department of Pathology, Cytology, and Experimental Medicine, Policlinico Umberto I°, University La
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