This review focuses on the mechanisms by which thyroid hormones affect the regulation of the cardiovascular system and the thermogenic and hemodynamic variation induced by thyroid disfunction. It is also stressed the hormonal role of the cardiac myocytes realising natriuretic peptides, involved in plasma volume homeostasis and cardiovascular remodelling; its rapid measurement is a useful clinical tool, in the diagnostic and prognostic of left ventricular dysfunction, correlating with the degree of the clinical symptoms. The endothelial layer is a receptor-effector endocrine organ that produces substances that maintain vasomotor balance and vascular-tissue homeostasis. Cardiovascular risk factors causes oxidative stress that alter endothelial function and leads to endothelial dysfunction. On the basis of the present body of evidence there is no doubt that endothelial dysfunction contributes to the initiation, and progression, of atherosclerotic disease and that it could be considered an independent vascular risk factor for the micro- and macrovascular damages in the diabetes disease. In several extrathyroidal pathological condition, as well as in heart failure, the main alteration of the thyroid function is referred to as "low T3 syndrome". This syndrome is due to an adaptative reaction of the metabolic pathway of thyroxine, producing an increased amount of rT3, metabolically inactive, thus decreasing the detrimental metabolic effects of T3, in conditions of critically impaired hemodynamic and metabolic efficiency. Preliminary clinical trials, in heart failure, suggest the prognostic value of the level of circulating T3, as well as usefulness of T3, or of thyromimetic derivatives (DITPA), in chronic treatment of the heart ventricular dysfunction.

Analyzing a cohort of 16,400 thyroid nodules, sequentially examined since 1982, the value of preoperative echo-guided fine needle aspiration cytology (FNA) in discriminating benign lesion from malignant ones, has been assessed. Ultrasonography provides a useful support not only to guide the diagnostic FNA methodology, but also monitoring therapeutic procedure: evacuation of cyst, alcoholic sclerotization, laser therapy, effects of treatment on the size of the nodular structure. The correct interpretation of the imaging pictures should be rationally anchored to both clinical criteria and to circumstantial anamnestic analysis, as well as to physical examination, laboratory tests, instrumental systems, cytomorphological patterns, immunohistologic and biomolecular studies. The FNA sampling under ultrasonography guidance offers an absolute diagnostic reliability, and it can be confidently applied for planning surgical strategy. By adopting this safe, non invasive, accurate diagnostic tool, that offers the advantage of eliminating unnecessary operation for benign lesions, the number of operation is strikingly reduced, while it allows to identify an higher surgical frequency of malignancy, yielding a prevalence of about 3% of thyroid nodules. FNA is a very profitable cost-effective diagnostic tool, reducing 20% the cost of care, for the evaluation and treatment of patient with thyroid nodule. Preliminary results on the molecular pattern of thyroid nodules, obtained applying a new methodological system, the Laser Capture Microdissection, are underlined; in the next issue of this journal it will be analytically illustrated the diagnostic role of this innovative procedure that appears very promising in obtaining information on the molecular derangements of a single thyroid cell, even at a precancerous stage; thus a preventive surgical treatment of a thyroid nodule genetically characterized can be predicted.

A careful pathological examination often reveals the presence of different lesions at various stages of tumor progression and invasion, even in those thyroid glands presenting with solitary nodules. Each thyroid lesion is composed of many different cell types, reflecting the marked heterogeneity of normal thyroid tissue. Among the different chromosome regions altered in thyroid tumors, 7q21 appears to be specifically involved in malignant tumors, especially of the follicular type. This study was conducted to analyze the loss of heterozygosity (LOH) pattern at 7q21 in pure populations of cells from each single lesion harbored in surgically removed thyroid glands, and to evaluate its clinical significance. One hundred and forty-two thyroid glands were examined, all showing, as a common trait, a goitrous appearance associated with one single lesion in 114 cases and with more than one in the remaining 28 cases. A total number of 318 lesions was analyzed, consisting of 142 goiters (TG), 48 hyperplasias (TH), 80 adenomas (TA) and 48 carcinomas (TC). Five different types of cells were isolated by laser capture microdissection from each lesion. DNA was analyzed by PCR and polyacrylamide gel electrophoresis in search of LOH affecting five microsatellite markers, D7S660, D7S630, D7S492, D7S657, and D7S689. We detected LOH at 7q21 not only in thyroid malignant tumors but also in benign lesions. Allelic loss occurred exclusively in dark nucleus and eosinophilic cytoplasm cells, commonly observed in the follicular type of lesions. In these types of lesions allelic loss frequency increases along with neoplastic transformation (9% in TG, 41% in TH, 68% in TA and 100% in TC), and is directly correlated with thyroid gland volume as well as with the presence of multiple lesions. The highest LOH rate was observed for D7S492, indicating that the recurrent region of deletion was localized at the corresponding genetic locus at 7q21.2, in the same position where the common fragile site FRA7E was previously mapped. LOH at this locus represents an early event in the development of follicular TC and is associated with intense growth of thyroid glands.

The insulin receptor susbtrate-3 (IRS-3) is a member of a family of intermediate adapter proteins that function as major intracellular targets for phosphorylation by the activated insulin and IGF-I receptors. Among the four IRS proteins identified so far, IRS-3 exhibits a rather peculiar expression pattern during both the embryonic development and adult life, suggesting a different mechanism of regulation of its expression. In this study, we cloned the 5' flanking region of the mIRS-3 gene and analyzed its promoter activity. The mIRS-3 promoter is inhibited by wild-type p53, and this effect is completely abolished by cotransfection of a dominant negative p53. Tumor-derived p53 mutants show variable, but lower suppressing capability than wt p53. In addition, treatment with doxorubicin inhibits endogenous expression of mIRS-3 mRNA in C2C12 and 3T3-L1 cells. The DNA region spanning from nucleotides -287 and -178 in the mIRS-3 promoter is responsible for a 32.2% reduction of the mouse double minute 2 (MDM2) promoter activity, suggesting its involvement in the p53-mediated inhibitory effect. In conclusion, our study demonstrates that the mIRS-3 promoter is regulated by p53 at the transcriptional level. The inhibition of mIRS-3 promoter by wild-type p53, and its de-repression by tumor-derived p53 mutants, appears to be similar to that previously reported for the IGF-I receptor promoter, suggesting a common role of these two genes in p53-mediated cell growth and differentiation.

We analyzed the structure and function of the 5' flanking region of the human type 2 deiodinase (hD2) gene. Two major transcription start sites were identified at -470/-474 from the ATG. The 5' flanking region of hD2 gene efficiently directed transcription in transient transfection studies, using luciferase as reporter gene, in HEK 293 cells. Basal transcriptional activity was significantly reduced by deleting the region containing a canonical cAMP-responsive element (CRE) located -766/-759 from ATG. Forskolin treatment significantly increased luciferase activity in cells transfected with CRE-containing constructs. This effect was abolished in constructs that did not contain CRE or contained the mutagenized CRE. Northern blot analysis in JEG-3 cells revealed that the hD2 messenger RNA was markedly increased after stimulation with cAMP agonist. The electrophoretic mobility shift assay with hD2-CRE probe and HEK 293 nuclear extract showed the occurrence of a DNA-protein complex, which was competed by specific unlabeled oligonucleotides and supershifted by the anti-CREB and anti-CRE modulator-1 antibodies. A-CREB, a dominant negative inhibitor of CREB, completely inhibited forskolin induction of the hD2 promoter. CREB protein, once cotransfected with hD2 promoter construct and pKA in F9 teratocarcinoma cells, which are unresponsive to cAMP, was able to stimulate the hD2 gene transcription. These results indicate the existence of a functional promoter within the 5' flanking region of hD2 gene which is characterized by the presence of a CRE. The specific involvement of CREB in the cAMP-mediated hD2 gene promoter induction also has been demonstrated.

The diagnostic algorithm of thyroid diseases, the most frequent dysendocrine condition, can be today integrated by the newly developed molecular methodologies. From the early diagnostic approaches, centered on the assessment of thyroid function, either by in vivo radioisotopic techniques, or by in vitro radioimmunological measurement of hormone plasma concentrations, it is nowadays possible to precisely define the molecular events triggered by the iodothyronine signal at the level of target tissues. In this brief review will be discussed the recent progresses on cloning and characterization of several genes involved in the regulation of thyroid differentiation, ability to trap iodine, synthesis and secretion of iodothyronines, regulation of thyroid function by TSH, transduction of the hormonal signal to subcellular structures involved in the translation of the hormone message in specific biological, effects such as those on metabolic homeostasis, cell proliferation and differentiation. It will be also discussed the most recent advancements on the genetics of thyroid diseases which have allowed to characterize the molecular basis of several thyropathies such as congenital hypothyroidism, thyroid hormone resistance syndrome, hyperthyroidism or hypothyroidism caused by TSH-receptor alterations, molecular abnormalities of oncogenes or tumor suppressor genes which are associated with benign or malignant thyroid cell transformation. The most recent developments of the diagnostic procedures of thyroid diseases, also in their pre-clinical stage, will be also reviewed together with a brief highlight on the most recent treatment options, centered on prophylactic therapeutic intervention or on the development of gene therapy strategies which will be possibly applied in a near future.

PCR-based strategies such as competitive RT-PCR or semiquantitative RTPCR are commonly used for quantitating low-abundance mRNA transcripts (4,7–9). Competitive RT-PCR relies on amplifying the same target with a known amount of a competitor/reference sequence and comparing the relative amounts of the two PCR products. To improve the sensitivity and accuracy of these methods, often expensive and cumbersome techniques such as HPLC or the use of radioactivity have been used for PCR product quantitation (1,2, 6,10). Ideally, a good competitor should share with the mRNA target the same primers and most of the sequence, and the resulting PCR products should be easily discernible from one another and quantified (5,11). Usually, a single target is quantified by competitive RTPCR, and several reactions would be needed to quantitate multiple target sequences in a given RNA sample. We present here a versatile method to synthesize competitor polyA-extended RNA sequences, which are ideal for multiplex RT-PCR in which reverse transcription may be primed with oligo dT. We show that this multiplex competitive RT-PCR approach can be used to detect mRNA species as low as 103 molecules/reaction. A rapid PCR-based method to synthesize internal standards for competitive PCR has been previously described (3). Briefly, the target sequences are amplified with two primers, one conventional sense primer (Figure 1A, primer a) to be used for the subsequent experiments and a modified antisense primer (Figure 1A, primer b1). The resulting PCR products, which by design are approximately 10% shorter than the target sequences (Figure 1A), are gel purified and reamplified with a second pair of primers containing, respectively, a HindIII site (sense primer) and oligo dT21 followed by an XbaI site (antisense primer) (Figure 1B). These two PCR amplification steps can be combined, but the required primers would be quite long and there would be a risk of poor amplification. The PCR products are then digested with the two enzymes, gel purified and directionally cloned into pGem4Z (Promega, Milan, Italy) (Figure 1C). The recombinant plasmids are linearized with XbaI, and RNA synthesis is performed in vitro using a commercially available kit (Riboprobe; Promega) with minor modification to the manufacturer’s instructions (Figure 1D). Briefly, 2 μg linearized plasmid is incubated in 40 mM Tris-HCl (pH 7.9 at 25°C), 10 mM NaCl, 6 mM MgCl2, 10 mM DTT, 2 mM spermidine, 0.05% Tween( 20, 0.5 mM each ATP, GTP, CTP and UTP and 40 U T7 RNA polymerase in a final volume of 100 μL for 2 h at 37°C. The samples are heated at 95°C for 2 min and placed on wet ice. Twenty microliters of the mixture is Benchmarks

OBJECTIVE: The selenoenzyme type 2 iodothyronine 5' deiodinase (DII) catalyzes the conversion of thyroxine into its active form tri-iodothyronine (T3), modulating thyroid hormone homeostasis in a local, tissue-specific manner. The amphibian, rodent and human cDNAs encoding this enzyme have been recently cloned and expressed. At present, little information regarding the genomic structure of mammalian DII is available. DESIGN AND METHODS: The complete structure, including intron-exon junctions, of the human DII (hDII) gene was obtained by long PCR and rapid amplification of cDNA ends (RACE). Chromosomal assignment of the hDII gene was performed by fluorescence in situ hybridization using a highly specific probe. RESULTS AND CONCLUSIONS: Our data demonstrated that hDII is a single copy gene located on chromosome 14, position 14q24.3. The gene spans over 15 kb, and the 7 kb transcript is encoded by three exons of 149 bp, 273 bp and 6.6 kb separated respectively by two 274 bp and 7.4 kb introns. A restriction map of the hDII gene is also reported. These data will help in further studies of the role of DII in the maintenance of peripheral thyroid hormone homeostasis.

OBJECTIVE: We have studied the effect of tryptophan on cellular [(125)I]tri-iodothyronine (T3) uptake by mouse thymocytes. MATERIALS AND METHODS: Mouse thymocytes (20 x 10(6 )cells/ml) were suspended in Krebs-Ringer solution buffered by Tris-HCl and incubation (23 degrees C at pH7.45+/-0.6), in the presence or absence of 1mM tryptophan, was started by adding 25 pM [(125)I]T3. At the end of incubation, samples were cooled in ice, centrifuged over a 30% sucrose cushion and the cell-associated radioactivity was measured in the pellet. RESULTS: Tryptophan reduced both the total and the saturable fraction of [(125)I]T3 uptake by 44% (P=0.0009) and 60% (P=0.0006) respectively, following 1 min of incubation. This effect was specific and dose-dependent, being maximal at 5mM concentration (-82%). In contrast, the pre-exposure of cells to tryptophan for up to 2h had no effect on the subsequent uptake of [(125)I]T3, in the absence of tryptophan. The effect of D-tryptophan on saturable T3 uptake was not different from that obtained using the L-stereoisomer. Tryptophan reduced the V(max) of the initial rate of saturable [(125)I]T3 uptake by two-thirds without affecting the apparent K(m) (2.2 nM) of the process, thus indicating the non-competitive nature of the inhibition. In sodium-free medium the saturable [(125)I]T3 uptake was reduced by 43%. The inhibitory effect of tryptophan on [(125)I]T3 uptake was exerted in both the presence and the absence of sodium. In fact, the inhibitory effect of tryptophan on T3 transport was greater and significantly different (P=0.0046) from that obtained by sodium depletion alone. CONCLUSIONS: Tryptophan interferes with both the sodium-dependent and -independent components of [(125)I]T3 uptake by a dose-dependent, non-competitive mechanism which operates in cis-modality at the plasma membrane level of mouse thymocytes.

The role of preoperative noninvasive diagnostic procedures in the management of benign thyroid diseases is critically reviewed and on the basis of a series of more than 13,000 thyroid nodules, sequentially examined, the role of preoperative fine needle aspiration (FNA) cytology in discriminating benign from malignant lesions, is assessed. Retrospective studies were performed to determine the diagnostic accuracy of FNA adopted as routine preoperative screening procedure as compared to intraoperative frozen section (FS) analysis. US-guided FNA was shown to be more accurate allowing the preoperative identification of occult or minimal carcinoma: in fact about 3% of malignant thyroid nodules were detected. Moreover, the operation time is reduced, and unnecessary surgical treatments for benign lesions are eliminated, preventing the need of two-stage cancer surgery. FNA is a cost-effective diagnostic tool with about 20% reduction in the cost of care of patients with thyroid nodules. Most recent methods of molecular biology which seem promising in thyroid tissue sampled by FNA to detect malignant lesions missed by conventional cytology and included in the generic category of "follicular proliferation", are analyzed.

BACKGROUND Atrophic body gastritis (ABG) has never been histologically characterized in patients with autoimmune thyroid disease (AITD), and its prevalence may be substantially different from that previously assessed based on only indirect evidence. OBJECTIVE To detect and characterize the presence of ABG in patients with AITD. METHODS Sixty-two patients with AITD (5 men and 57 women), aged between 21 and 74 years, have been screened for the presence of ABG by assaying serum gastrin levels. Patients with hypergastrinemia underwent gastroscopy followed by the histological examination of multiple biopsy specimens. The diagnosis of ABG was based on hypergastrinemia and pentagastrin-resistent achlorhydria, confirmed by histological examination. RESULTS Twenty-two (35%) of 62 patients had hypergastrinemia (mean +/- SEM gastrin level, 1070+/-288 pmol/L). The diagnosis of ABG has been histologically confirmed in all 22 patients, and the score of atrophy was moderate to severe. In group A (patients aged 20-40 years; n = 21), 6 patients (29%) had ABG, compared with 11 patients (37%) in group B (patients aged 41-60 years; n = 30) and 5 patients (45%) in group C (patients aged 61-80 years; n = 11). Antiparietal cell antibodies were detected in only 68% (15/22) of patients with ABG. Anemia was observed in 82% (18/ 22) of patients with AITD and ABG but only in 22% (9/40) of patients without ABG (P<.0001). CONCLUSIONS In the patients with AITD studied, about one third had ABG, which was diagnosed also in young patients; the measurement of gastrin levels represented the most reliable tool in the diagnosis of ABG; and the presence of anemia, even microcytic, was suggestive of undiagnosed ABG.

Type II 5′-Deiodinase (5′DII) is a key element in the maintenance of peripheral thyroid hormone homeostasis through the regulation of local T4 to T3 conversion in pituitary, brain, brown adipose tissue and placenta. The cDNA containing the coding region of the human 5′DII (HDII) has been recently cloned from infant brain. In the present paper we report the genomic structure, chromosomal localization and restriction map of the coding region of HDII. The presence of a single intron located at codon 75 was demonstrated using a PCR-based strategy; the exon–intron junctions were then cloned and partially sequenced. Chromosomal localization was performed by radiation hybrid mapping. This study demonstrated that the entire coding region of the HDII gene is contained in two exons spliced at codon 75 by a 7.4 Kb intron and that the HDII chromosomal location is 14q24.3. These data will allow further studies of the role of HDII in the pathophysiology of thyroid homeostasis.

Fine-needle aspiration biopsy (FNAB) is an accurate, slightly invasive, and safe method for the preoperative diagnosis of thyroid nodules. Recently, ultrasound guidance has been suggested as a valuable aid to enhance FNAB diagnostic performance. In this study, we have compared diagnostic accuracy of conventional FNAB (C-FNAB) versus sonography-guided FNAB (SG-FNAB) on a large sample population of 9683 patients with thyroid nodules. Over a 15-year period, 4986 patients were investigated by C-FNAB and 4697 underwent SG-FNAB. A valid cytological diagnosis was obtained in 85.9% of C-FNAB and in 91.5% of SG-FNAB cases, allowing detection of thyroid cancer in 1.6% and 2.1% of patients, respectively. The indeterminate pattern of follicular neoplasia was observed in 238 C-FNAB (5%) and in 272 (5.4%) SG-FNAB nodules. Specimens were cytologically inadequate in 433 C-FNAB (8.7%), but only in 167 SG-FNAB cases (3.5%). A total of 535 C-FNAB and 540 SG-FNAB nodules underwent surgery. False-negative results occurred in 7 C-FNAB nodules (2.3%), but only in 3 SG-FNAB cases (1%). Sensitivity, specificity, and global diagnostic accuracy of C-FNAB compared with SG-FNAB were 91.8% versus 97.1%, 68.8% versus 70.9%, and 72.6% versus 75.9%, respectively. Our results, based on a large population of thyroid nodules, demonstrate that SG-FNAB allows a more precise and adequate sampling of thyroid nodular lesions and is associated with a lower rate of false-negatives, thus improving global diagnostic accuracy in the preoperative selection of thyroid cancer.

Factor XII (FXII) is a liver-specific zymogen involved in the regulation of hemostasis, particularly in the activation of fibrinolysis. Transcription of the FXII gene is stimulated by estrogens through specific interaction of the estrogen receptor alpha (ER alpha) with an estrogen response element present on FXII promoter. Interestingly, the magnitude of ER alpha induction in liver HepG2 cells is much lower than in NIH3T3 fibroblasts, suggesting that cell-specific factors may modulate ER alpha-dependent trans-activation. Comparative footprinting analysis of FXII promoter (from nucleotides -181 to +49) in liver vs. non-liver cell environments allowed identification of four deoxyribonuclease I-protected sites only in the presence of HepG2 nuclear extracts. Computerized homology search identified sites III and IV as consensus binding sequences for the liver-enriched transcription factor hepatocyte nuclear factor-4 (HNF-4), formerly an orphan receptor belonging to the superfamily of steroid/thyroid hormone nuclear receptors. In transient transfection assays in NIH3T3 cells, HNF-4 significantly inhibited (70%) estrogen induction of FXII promoter while not affecting basal promoter activity. Conversely, HNF-4 did not inhibit estrogen inducibility of FXII promoter in HepG2 cells due to the high endogenous levels of HNF-4 protein. In gel shift assays, HNF-4, either present in HepG2 nuclear extracts or generated by in vitro transcription/translation, specifically bound FXII promoter. This interaction is strictly required in eliciting the antagonistic effect because in NIH3T3 cells, selective mutations of sites III and IV abrogated HNF-4 inhibitory properties. In the liver-specific environment, the same mutant construct exhibited higher estrogen-dependent inducibility compared with native promoter. Rescue of estrogen responsiveness was also achieved using a dominant negative HNF-4, which counteracted endogenous HNF-4 activity. In conclusion, our findings address a direct role for HNF-4 in modulating estrogen-dependent transcription of the FXII gene promoter.

The relation between thyroid homeostasis and the biochemical parameters of subclinical protein malnutrition has been analyzed in schoolchildren in a rural area in the south of Italy, known to be moderately iodine-deficient. The sera of 32 children (15 males and 17 females aged 6 to 11 years) have been analyzed. These children were divided into two groups, according to thyroid function: (1) 16 euthyroid children (mean thyrotropin [TSH] 2.38 +/- .35 mU/L; 6 with goiter) and (2) 16 subclinical hypothyroid children (mean TSH 7.32 +/- 1.68 mU/L; 6 with goiter). Retinol circulating complex (RCC) components were determined in serum by high-performance liquid chromatography (HPLC) and radial immunodiffusion and the essential and nonessential amino acid levels by ion exchange chromatography. Reduced retinol binding protein (RBP) and transthyretin (TTR) levels were recorded in the sera of 11 of 32 (34%) and in 5 of 32 (16%) patients, respectively. The linear regression analysis revealed that RBP and TSH levels were inversely correlated (r = -0.514; p < 0.0026). The RBP levels were subnormal in 2 of 16 euthyroid and in 9 of 16 hypothyroid patients (Fisher test p < 0.023), and the mean RBP levels were significantly reduced in the hypothyroid patients when compared with those of the euthyroid group (p < 0.0026). The retinol/RBP ratio was also significantly different between euthyroid and hypothyroid children (0.75 vs. 0.95; p < 0.0002). The mean essential amino acid levels, with the exception of methionine, were all in the normal range. The selected amino acid ratios confirmed that the patients were exposed to mild protein malnutrition. These results provide evidence that even mild protein-energy malnutrition may have detrimental effects on thyroid homeostasis in iodine-deficient areas.

Alterations of the tumor suppressor gene p53 are uncommon in differentiated thyroid neoplasia but are detected at high frequency in anaplastic thyroid carcinoma suggesting that impaired p53 function may contribute to the undifferentiated and highly aggressive phenotype of these tumors. Effects of wild type p53 (wt-p53) re-expression were investigated in a human anaplastic thyroid carcinoma cell line (ARO) expressing a mutated p53. ARO cells were stably transfected with the temperature-sensitive p53 Val135 gene (ts-p53) which exhibits wild type-like activity at 32°C. Exogenous wt-p53 function in ARO-tsp53 clones was assessed by evaluating its transcriptional activity on a CAT reporter vector containing p53 binding sites. At 32°C, a significant reduction in the proliferation rate (≈percnt;50%) was observed, with accumulation of cells in the G0/G1 phase of the cell cycle. This effect was accompanied by induction of the expression of the growth inhibitor p21/Waf1 gene. At 32°C, ARO-tsp53 clones also showed a marked impairment of their tumorigenic potential. Furthermore, transfected clones re-acquired the ability to respond to thyrotropin (TSH) stimulation showing an increased expression of thyroid-specific genes (thyroglobulin, thyroperoxidase and TSH receptor). In conclusion, re-expression of wt-p53 activity in ARO cells, inhibits cell proliferation and restores responsiveness to physiological stimuli.

The natural history of Hürthle cell (HC) lesions has been the focus of a considerable debate. The difficulties in defining the malignant potential of HC has led to the current designation of HC tumor, with the implication that it may behave as either a benign or a malignant lesion. The objective of our study was to verify the clinical and prognostic relevance of the cytological diagnosis of HC in the thyroid lesion, 10,950 consecutive patients (F/M = 5.6/1) with thyroid nodules were evaluated by means of fine needle aspiration biopsy (FNAB). Cytological diagnosis showed the presence of HC in 285 cases (2.6%), with a F/M ratio of 8.2/1. In 123 cases (43.2%) cytologic diagnosis resulted benign. A suspicious pattern of follicular neoplasm was observed in 159 cases (55.8%). Only in 3 cases (1%) thyroid carcinomas were preoperatively identified. No false positive or negative cases were observed. Among the HC lesions, 85 patients (29.8%) underwent thyroid surgery because of a malignant or suspicious cytologic diagnosis, continuous nodular growth despite LT4 therapy, mechanical compression or clinical judgement. The other two hundred patients were clinically evaluated and, one year later, repeated FNAB confirmed the cytologic diagnosis of benignity. Among the follicular neoplasm nodules, 80 cases (55.3%) were surgically explored, and thyroid carcinoma diagnosed in 30 of them (37.5%), this percentage being greater than that observed in the group of non-HC follicular neoplasm (17%). Pathologic criteria for malignancy (vascular invasion, transcapsular penetration, destructive capsular invasion) were described in 25 out of all carcinomas.