Evaluation of the fine needle aspiration biopsy in the preoperative selection of cold thyroid nodules

Preoperative evaluation and predictive value of fine-needle aspiration and frozen section of thyroid nodules

BACKGROUND

We sought to evaluate the predictive value of preoperative fine-needle aspiration (FNA) on surgical decision making by evaluating the final pathologic diagnosis and comparing it to the preoperative diagnosis. Further, we wished to calculate the predictive accuracy of each of several types of preoperative FNA diagnosis.

STUDY DESIGN

A retrospective chart review of 151 thyroid resections between July 1990 and April 1996 at the University of Virginia was undertaken. The mean age was 45 years (range, 11 to 85 years). Preoperative laboratory values, presenting symptoms, imaging studies, and predictive values of preoperative FNA and intraoperative frozen section were analyzed.

RESULTS

Symptomatology was poorly predictive of a benign versus malignant postoperative final pathologic diagnosis. Sensitivity, specificity, and accuracy of frozen section versus FNA was 86% versus 86%; 99% versus 93%, and 96% versus 92%, respectively, if the reading "cancer" or "suspicious" were predicted as positive for malignancy and "benign" or "follicular" were predicted as negative for malignancy. If only the reading "cancer" was predicted as positive for malignancy and only "benign" was predicted as negative for malignancy, sensitivity and specificity for FNA were 100% and 96%, respectively, and 100% and 99%, respectively, for frozen section. Forty-nine "follicular" lesions obtained by preoperative FNA resulted in 46 benign diagnoses after surgical resection.

CONCLUSIONS

The use of preoperative FNA is a powerful diagnostic tool in the hands of skilled pathologists. There is increasing evidence that intraoperative frozen section adds little to intraoperative decision making in patients diagnosed with thyroid cancer by preoperative FNA. Less definitive interpretations decrease the sensitivity, specificity, and accuracy of the FNA diagnosis.

Refined use of scintigraphy in the evaluation of nodular thyroid disease

BACKGROUND

Scintigraphy has been advocated in patients with a thyroid nodule when fine needle aspiration biopsy (FNAB) is not definitive. The purpose of this study was to determine the incidence of hyperfunctioning nodules in patients without a definitive FNAB, the correlation of serum thyrotropin (TSH) levels with the functional status of a nodule, and whether a sensitive TSH assay can be used in lieu of scintigraphy.

METHODS

From 1990 to 1996, patients with a thyroid nodule were evaluated with FNAB and serum TSH measurement. Iodine-123 scintigraphy was reserved for patients without a definitive FNAB and was correlated with TSH levels.

RESULTS

Of 356 patients with a thyroid nodule, 102 did not have a definitive FNAB. A hyperfunctioning nodule was diagnosed in 14 of the 102 patients. A low TSH level was detected in 12 (86%) of 14 patients with a hyperfunctioning nodule (mean = 0.04 +/- 0.38 microIU/mL) and only 20 (23%) of 88 patients with a hypofunctioning nodule (mean = 0.87 +/- 4.11 microIU/mL) (P < .05). Only 2 of 70 (2.8%) patients with a normal or increased TSH level had a hyperfunctioning nodule.

CONCLUSIONS

A 14% incidence of hyperfunctioning nodules in patients without a definitive FNAB warrants the use of scintigraphy but only when serum TSH levels are low, thus avoiding unnecessary scans in 91% of patients with a thyroid nodule.

Outcome of differentiated thyroid cancer in Graves' patients

The clinical behavior and outcome was evaluated in 21 nonoccult differentiated thyroid carcinomas occurring in Graves' patients during the period 1982-94 and compared with that of matched tumors occurring in euthyroid controls (n = 70). At surgery, patients with Graves' disease showed distant metastases more frequently than euthyroid patients (3/21 = 14.3% vs. 1/70 = 1.4%, P = 0.0556). Graves' patients also showed a significantly higher cumulative risk of recurrent/progressive distant metastases or total adverse events (odd ratios = 3.14 and 2.07, respectively) as compared with euthyroid patients. At the last follow-up visit, persistence of distant metastases was also more frequent in the Graves' group (P = 0.007), although the cumulative individual dose of radioiodine administered was higher than in the control group (median dose = 805 mCi vs. 350 mCi). Two patients died in the Graves' group vs. none in the control group. Circulating thyroid stimulating antibodies were present in all patients but one and persisted as long as signs of disease were evident. These findings indicate that differentiated thyroid carcinomas in patients with Graves' disease are more aggressive than those occurring in matched euthyroid controls and should, therefore, be managed accordingly.

Diagnostic accuracy of conventional versus sonography-guided fine-needle aspiration biopsy of thyroid nodules

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.

User of fine-needle aspiration biopsy and frozen section in the management of the solitary thyroid nodule

BACKGROUND

This study evaluates the indication for frozen section (FSx) in the management of the solitary thyroid nodule given the increasing use of fine-needle aspiration biopsy (FNAB).

METHODS

The charts of 561 patients who underwent thyroidectomy for a solitary nodule were reviewed. Each patient underwent either FNAB, FSx, or both. Results were compared to the final diagnosis to evaluate their effectiveness in predicting malignancy.

RESULTS

The sensitivity and specificity for FNAB alone (162 patients) were 86% and 91%, respectively, and for FSx (494 patients) 79% and 99%, respectively. The routine use of FSx with diagnostic FNABs did not improve the accuracy over either test alone. Sensitivity, specificity, and accuracy were essentially unchanged when the use of FSx was limited to just atypical FNAB but dropped significantly when FSx was not used.

CONCLUSIONS

When results of FNAB and FSx are interpreted as benign or malignant, both are highly accurate predictors of malignancy. Routine use of FSx and FNAB does not improve the sensitivity or specificity in the detection of malignancy over that of either examination alone. FSx proved useful in determining the extent of operation only when results of the FNAB were atypical.

Incidence and clinical characteristics of thyroid carcinoma after iodine prophylaxis in an endemic goiter country

Iodized salt prophylaxis has been performed in Austria since 1963. Through this approach, mean urinary iodine excretion has been normalized to 144+/-23.5 microg/g creatinine per day. Thus Tyrol is no longer an endemic goiter area. We have analyzed the impact of iodized salt prophylaxis on thyroid cancer (TC) comparing data from the early 1960s with those corresponding to the period 1986 to 1995, when iodine supply was normalized. The study included 439 patients from Tyrol and Southern Tyrol. The incidence of TC in Tyrol has risen during the past decades from 3.07 between in 1957 and 1970 to 7.8 between 1990 and 1994 (CR/100000/year). We observed a rise in the percentage of differentiated adenocarcinomas (56% to 91.5%) with a predominance of papillary TC (54.4%) along with a decrease of anaplastic TC. In addition to these histological features, a shift to less advanced TNM stages, eg, T1-3, N0-1a, M0, was obvious, increasing from 29% to 72.2%, whereas advanced tumors, ie, T4 or N1b or M1, decreased from 71% to 28%. These changes have significantly improved prognosis. The current 5-year survival rate is 90.7% as compared with a rate of 73% in the 1960s; the values for 7-year survival are 89% and 48%, respectively. The marked effects of age, tumor stages, and histology on prognosis were confirmed with the Kaplan-Meier method. We conclude that together with normalization of iodine supply in an endemic goiter region the epidemiological profile of TC has changed. Even though the incidence of TC has risen, prognosis has significantly improved due to a shift towards differentiated forms of TC that are diagnosed at earlier stages.

Fine-needle aspiration biopsy of thyroid nodules: impact on clinical practice

The aim of the present study was to analyze the changes in our clinical practice due to the use of FNAB in the management of nodular thyroid disease. Patients attended the thyroid unit for thyroid nodules. The study comprises three periods: First, from January 1980 to May 1984, 226 patient. Second, from June 1985 to December 1990, 166 patients. Third, from January 1991 to December 1993, 403 patients.

DESIGN

retrospective the 1st period and prospective the 2nd and 3rd periods. During the 1st and 2nd periods, decision for surgery was based on clinical parameters together with results of 99Tc radionucleotide scan and B mode ultrasound studies. In the 3rd period surgical decision was based principally on cytologic results. We comparatively studied the frequency of surgical operation and frequency of malignancy in surgical thyroid specimens between the study periods. Determination of sensitivity, specificity and accuracy of the diagnostic methods was done. We observed a decrease in the frequency of patients requiring surgery, 89.9%, 67.8% and 46.6% for the 1st, 2nd and 3rd study periods, X2 = 114.7, p < 0.0001; and an increase in the frequency of malignancy in the surgical specimens, 14.7%, 24.4% and 32.9% for 1st, 2nd and 3rd periods respectively, X2 = 4.5, p < 0.05. The sensitivity 92.5% and 93.5%, the specificity 50.6% and 61.1%, and the accuracy 60.9% and 71.8% of the FNAB for the second and third periods respectively. The rates of false negative cytological specimens were 1.8% and 2.1% for 2nd and 3rd respectively, p > 0.05. Since the introduction of FNAB in the evaluation of our patients around 70% of these had a definitive preoperative diagnosis of either benign or malignant disease. Simplification in management of patients with nodular thyroid disease is the most important impact for the use of FNAB. Furthermore, a decrease in the number of patients requiring surgical treatment and an increase of malignant nodules in the specimens obtained by surgery were also observed. We think that FNAB is the most direct and accurate method in the management of patients with thyroid nodules.

[Reliability of needle biopsy of solitary thyroid nodules in view of surgical indications]

To evaluate the accuracy of fine-needle biopsy in the management of the solitary thyroid nodules, 320 biopsies without aspiration were performed in 212 patients, iteratively in 91 cases. Among the 212 initial biopsies, 93 smears were found presumably benign (43.9%), 6 malignant (2.8%), 49 benign implying cytologic control (23.1%), 24 suspicious with decision to operate (11.3%), 40 inadequate (18.9%). On 67 surgical indications (malignant or suspicious cytology, or clinical data), 59 operations were performed. The 11 diagnosed cancers (5.2% of the patients; 18.6% of the operations) correspond to six malignant and five suspicious cytologies at the first or second biopsy. On 145 cases without decision to operate, 125 were clinically surveyed, with sometimes another biopsy (mean survey: 27.6 months; range: 6-80 months), and it was never necessary to modify the initial expectancy attitude. Our results, rather similar to those related by most of the previous publications, confirm that the fine-needle biopsy is a reliable and effective means for the etiologic diagnosis of thyroid nodules and the indications for operative intervention. It spares many patients from a useless operation and is worthy to take a leading place in exploring these nodules.

Selective expression of CD44 cell-adhesion molecule in thyroid papillary carcinoma fine-needle aspirates

Recent descriptions of numerous pitfalls in the cytologic diagnosis of thyroid papillary carcinoma on fine-needle aspiration biopsy specimens have prompted studies of new ancillary diagnostic methods. We evaluated the potential use of immunocytochemical staining of thyroid fine-needle aspiration biopsy specimens for CD44, a glycosylated cartilage link protein associated with extracellular matrix adhesion and lymphocyte homing. Fourteen of 16 (88%) classic, surgically confirmed, thyroid aspiration biopsies stained intensely positive for this marker, whereas 0 of 30 (0%) similarly-processed benign aspirates from colloid nodules showed immunoreactivity for CD44 antigen. From this study, we conclude that most papillary carcinomas of the thyroid express the celladhesion molecule CD44, which may be of clinical value in confirming the diagnosis on borderline fine-needle aspiration specimens. Further study of CD44 expression may prove of significant interest in explaining the unusual mode of spread and clinical course of this disease.

An update on diagnostic methods in the investigation of diseases of the thyroid

Iodine deficiency and iodine-deficiency disorders continue to be problems in several parts of Europe, requiring further improvements in the techniques employed in thyroid diagnosis, and particularly in the early diagnosis and risk assessment of autonomously functioning thyroid tissue. For the latter purpose, scintigraphy with technetium-99m pertechnetate under exogenous or endogenous thyroid-stimulating hormone (TSH) suppression provides the best results. Significant methodological improvements in laboratory tests have resulted from the application of new luminescent techniques and gene technology to thyroid function tests. Especially TSH measurement using second- or third-generation assays ensures diagnostic accuracy, so that the thyrotropin-releasing hormone (TRH) test is now almost always unnecessary. The differentiation of blocking and stimulating TSH receptor antibodies is relevant when discrepant results are obtained with respect to thyroid function. Determination of glycosaminoglycans in urine may become a helpful tool in the follow-up of endocrine ophthalmopathy. Some new imaging agents have recently been applied in the scintigraphy of thyroid diseases, such as octreotide, or in thyroid diagnosis, such as fluorodeoxyglucose. Both improve the detectability of metastases of thyroid cancer, especially if the radioiodine scan is negative.

Thyroid imaging with Tc-99m MIBI in patients with solitary cold single nodules on pertechnetate imaging

Thyroid imaging was performed in 30 patients with the standard pertechnetate technique, as well as with Tc-99m MIBI using a double-phase acquisition protocol. All patients had normal thyroid function confirmed by hormone measurements and cold solitary thyroid nodules, which were evaluated by pertechnetate scanning. Tc-99m MIBI scans were reported as showing cold (N = 14), warm (N = 7), or hot (N = 9) nodules. Nodule classification was made according to fine needle aspiration biopsy findings in 20 patients. The remaining 10 proceeded to surgery and had histopathologic confirmation of their lesions. Although all cold nodules with Tc-99m MIBI were cystic, six of the warm nodules were benign lesions. No histologically proven benign nodule was hot with Tc-99m MIBI. Of the hot nodules, seven were suspicious for follicular carcinoma with fine needle aspiration biopsy (N = 3), or had histologically proven papillary carcinoma (N = 4). Delayed images in five of seven of these lesions showed nodular retention of the radiopharmaceutical. In conclusion, double-phase Tc-99m MIBI scanning of the thyroid gland could be helpful in the preoperative assessment of patients with cold solitary thyroid nodules in order to evaluate the malignancy probability of these lesions.

Aspiration needle biopsy refines preoperative diagnosis of thyroid nodules defined at fine needle aspiration as microfollicular nodule

The aim of this paper was to verify the hypothesis that large needle biopsy performed preoperatively can refine preoperative fine needle aspiration (FNA) cytological diagnoses of microfollicular nodules. Since 1980 we have been using FNA and aspiration needle biopsy (ANB) (18 or 16 gauge needles) to select for surgery all euthyroid patients with palpable thyroid nodules referred to our department. From 1980 to 1994, 6,124 patients (12% male, 88% female) with thyroid nodules (71% single, 29% multiple) were examined by FNA; 29% of these patients were also examined preoperatively by ANB histology. Of all the nodule patients examined, 371 received a preoperative FNA diagnosis of microfollicular nodule. Two hundred and fifty-four of these nodules (68%) were also examined preoperatively by ANB. Unsatisfactory ANB specimens constituted 17% of cases; pure microfollicular structure was confirmed by ANB in 36% of the nodules; ANB showed the remaining 47% to contain a macrofollicular component, thus suggesting a benign hyperplastic lesion. Twelve nodules which were found to be microfollicular at FNA cytology and micro-macrofollicular at ANB were excised and were subsequently determined as benign at definitive postoperative histology. These data indicate the utility of ANB in refining the preoperative FNA diagnosis of microfollicular nodule and in preoperatively identifying benign hyperplastic mixed micro-macrofollicular lesions which can be followed by observation.

Controversies in the management of cold, hot, and occult thyroid nodules

Some aspects of thyroid nodule evaluation and management remain controversial. Radionuclide scanning provides functional information about nodules and differentiates cold from hot nodules. Although thyroid cancers are cold on scan, most cold nodules are benign. Ultrasonography visualizes the thyroid gland and nodules with remarkable clarity and provides structural information about location, number, size, and consistency of nodules. Widespread application of ultrasonography has resulted in the frequent discovery of incidental (occult) nodules in the general population. The clinical significance of these nodules remains unknown, and their management has created a dilemma for physicians. Current cost-effective evaluation of nodules does not include scanning or ultrasonography as routine frontline tests. In most centers, fine-needle aspiration biopsy has supplanted imaging studies as the routine initial procedure for differentiating benign from malignant nodules. Cytologic diagnosis is reliable and inexpensive, and it results in a better selection of patients for surgery. Limitations include false-negative diagnoses, nondiagnostic results, and indeterminate "suspicious" results. Laboratory test results are usually normal, but determination of serum thyrotropin may identify a hot nodule, and plasma calcitonin may help diagnose medullary thyroid carcinoma. Treatment of thyroid nodules is controversial. In some practices, benign colloid nodules are treated with suppressive doses of levothyroxine. Recent reports cast doubt on the efficacy of this approach, and it is no longer acceptable to select patients for surgical treatment on the basis of suppressive therapy. Furthermore, suppressive levothyroxine therapy may be associated with significant bone and cardiac side effects, especially in elderly patients and postmenopausal women. Our approach is observation for most patients, and we suggest a careful risk-benefit analysis when suppression is considered. Hot (autonomous) nodules can be treated with radioiodine, surgery, or ethanol injection. The use of sensitive thyrotropin assays has revealed that the "euthyroid" hot nodule is often associated with subclinical hyperthyroidism, warranting treatment if risks of osteoporosis are significant. Small (< 1.5 cm) occult nodules can be observed. Larger (> 1.5 cm) nodules can be selectively evaluated by ultrasonographically guided fine-needle aspiration. It is prudent to consider cost of care, risk-benefit analysis, and the low incidence of malignancy in thyroid nodules when diagnostic tests are selected and the treatment plan is outlined.

Cost-effective evaluation of the patient with a thyroid nodule

Although thyroid nodules are common, less than 5% prove to be malignant. Because of its accuracy, simplicity, and low cost, FNAC has virtually replaced ultrasonography and radionuclide scintigraphy as the primary diagnostic procedure in the evaluation of the patient with a thyroid nodule. In studies comparing preoperative cytodiagnosis with histopathologic diagnosis, the predictive values of benign, malignant, and indeterminate cytodiagnoses averaged 94%, 96%, and 73%, respectively. Guidelines for a cost-effective approach to management of the patient with a thyroid nodule are presented. With a benign cytodiagnosis, follow-up with repeat FNAC in about 1 year is recommended. For the nodule with malignant or indeterminate cytology, surgical resection is indicated. Surgical resection is also indicated for the cyst that recurs after aspiration, as FNAC is less reliable owing to the paucity of cells. FNAC has less diagnostic utility in the evaluation of a nodule with clinical features suggesting malignancy, a nodule that is present in the diffuse toxic goiter of Graves' disease, or a nodule that is found in a patient with a history of radiation to the head, neck, or chest. In these circumstances, surgery is indicated irrespective of the cytologic findings.

Thyroid biopsies: fine-needle aspiration biopsy versus spring-activated core biopsy needle in 102 patients

PURPOSE

Use of the single-action spring-activated core biopsy needle was compared with the fine needle aspiration biopsy (FNAB) technique in ultrasound (US)-guided thyroid biopsies.

PATIENTS AND METHODS

Results in 102 patients who underwent sonographically guided thyroid biopsies with both fine needles and core biopsy needles were prospectively evaluated. Results from the 21-gauge FNAB (n = 102) were compared with results from 18-gauge (n = 1), 19-gauge (n = 2), 20-gauge (n = 43), or 21-gauge (n = 56) single-action spring-activated core biopsy needles.

RESULTS

If the suggestive and diagnostic results were combined, the diagnostic accuracy for the core biopsy needle was 90.2% (92 of 102) and was 80.3% (82 of 102) for FNAB (P = .048). The diagnostic accuracy for the combination of both needles was 97.1% (99 of 102). The complication rate was 0.98% (n = 1). This complication was a minor soft-tissue infection successfully treated with orally administered antibiotics.

CONCLUSION

In summary, sonographically guided biopsies of the thyroid performed with single-action core biopsy needles are safe and effective. The results with use of these needles are better than the results of FNAB, but the best results are obtained when both needles are used in the same patient.

Thyroperoxidase immunodetection for the diagnosis of malignancy on fine-needle aspiration of thyroid nodules

We have previously demonstrated that in 95.6% of malignant thyroid tumors the enzyme thyroid peroxidase (TPO) presents antigenic changes detectable by a monoclonal antibody termed MoAb47. The aim of this study was to investigate the interest of TPO immunodetection for the diagnosis of malignancy on fine-needle aspiration biopsy (FNAB) of thyroid nodules. The study was performed on 300 patients. Slides of FNAB aspirate were air-dried and stained by anti-TPO-MoAb47. According to the percentage of TPO-positive epithelial cells, patients were divided into two groups: benign (> 80%) and malignant (< 80%). In 279 cases additional slides were available for Giemsa stain and standard cytology. All the patients were operated on, and the final diagnosis was recorded as benign in 248 cases (183 macrofollicular nodules, 23 microfollicular adenomas, 18 atypical adenomas, 11 oncocytomas, 11 thyroiditis, 2 Graves' disease) and malignant in 52 cases (44 papillary carcinomas and 8 follicular carcinomas). Samples from 215 of 248 benign nodules yielded 80% to 100% TPO-positive cells, whereas samples from all malignant tumors yielded less than 80% positive cells. The sensitivity of TPO staining for diagnosis of malignancy was thus 100%, its specificity 86.7%, and its overall accuracy 89%. With conventional cytology, sensitivity, specificity, and accuracy were 91.6%, 79.2%, and 81.0%, respectively. We conclude from this study that TPO staining with MoAb47 should become an essential adjunct in the preoperative cytologic diagnosis of thyroid nodules.

Diagnostic pitfalls in thyroid fine-needle aspiration: a review of 394 cases

To determine the diagnostic pitfalls of thyroid fine-needle aspiration (FNA), we reviewed 394 thyroid aspirates obtained between January 1986 and December 1990. Surgical follow-up was available for 150 aspirations. The cytologic diagnoses were categorized into four groups: benign, 57; indeterminate, 51; malignant, 33; and nondiagnostic specimen, nine. There were three false negative diagnoses (3%), which upon review were judged to be inadequate specimens. Three false positive diagnoses (7%) were identified: in the first two cases, follicular adenomas were mistaken for papillary carcinoma; in the third case, atypical Hürthle cells were mistaken for a Hürthle cell carcinoma. Our results showed a sensitivity of 93% and a specificity of 91% for the detection of malignancy. If indeterminate cases were considered positive, the specificity decreased to 50%, while the sensitivity increased to 97%. We conclude that: 1) certain follicular adenomas may display cytologic features mimicking papillary carcinoma; 2) as in follicular neoplasms, aspirates of Hürthle cell adenomas cannot be differentiated from Hürthle cell carcinomas; 3) with adequate sampling, false negative results can be markedly reduced.

Cancer risk in patients with cold thyroid nodules: relevance of iodine intake, sex, age, and multinodularity

PURPOSE

We evaluated the frequency of thyroid cancer in patients with cold thyroid nodules in relation to iodine intake, sex, age, and multinodularity in a consecutive series of patients with nodular thyroid diseases.

PATIENTS

In the period from 1980 to 1990, 5,637 patients were studied: 4,176 patients were from an iodine-sufficient area (ISA) and 1,461 from an adjacent iodine-deficient area (IDA). Surgery was performed in 792 patients on the basis of a suspicious or malignant finding at fine-needle aspiration biopsy.

RESULTS

The overall thyroid cancer frequency was 4.6% (259 patients had cancer). Iodine intake affected the cancer rate in patients with cold nodules. The frequency of cancer in patients with cold thyroid nodules was 5.3% in the ISA and 2.7% in the IDA. This difference, however, was significant only in females. Sex had a major influence on the malignant rate of cold nodules; although female patients were more frequently observed (n = 5,028) than male patients (n = 609), the frequency of cancer was significantly lower in female patients with cold nodules (4.2%) than in males (8.2%). Age was an important factor in both sexes. The proportion of nodules that were malignant was smallest in patients of the 4th decade and was greatest in patients younger than 30 years or older than 60 years. Multivariate analysis showed that sex and age interact in determining the cancer risk in patients with thyroid nodules. Finally, the frequency of thyroid cancer in patients with a solitary nodule was not different from the frequency in patients with multiple nodules.

CONCLUSION

Our study indicates that thyroid cancer risk in a patient with a nodular goiter varies markedly according to iodine intake, sex, and age but not in relation to multinodularity, as assessed by clinical examination. The knowledge of these epidemiologic aspects of thyroid cancer may increase the accuracy of the preoperative selection of patients with cold nodules of the thyroid.