Nonpalpable Thyroid Research Articles

Usefulness of Ultrasound-Guided Fine-Needle Aspiration Cytology in the Diagnosis of Non-Palpable Small Thyroid Nodules

Diverse and contradictory approaches have been suggested for the management of non-palpable thyroid nodules. The aim of our study was to evaluate the indications and limits of ultrasound-guided fine-needle aspiration cytology (US-FNAC) in non-palpable infracentimetric thyroid nodules. From September 2003 to December 2004 we observed 325 patients with non-palpable thyroid nodules. We divided our series into three groups according to the diameter of the lesion in order to verify the effectiveness of US-FNAC for lesions of less than 1 cm. We assessed the cases with satisfactory and unsatisfactory results in the three groups into which the sample was divided (4 mm to 1 cm; 10.1 mm to 15 mm, and 15.1 mm to 25.5 mm). Our statistical analysis by means of the z-test showed there was no significant (5%) difference in the percentage distribution of the unsatisfactory results in the three groups. Fine-needle cytology appears to be a useful diagnostic tool also for nodules of less than one cm because the percentage of unsatisfactory results is not related to the size of the nodule.

Thyroid Evaluation in Patients with Primary Hyperparathyroidism

We evaluated the efficacy of preoperative high-resolution ultrasonography (US) for diagnosing possible concomitant thyroid disease which affects the surgical management in patients with primary hyperparathyroidism (pHPT). One hundred and nine patients with sporadic pHPT underwent US with or without ultrasound-guided fine-needle aspiration biopsy (US-FNAB). Diagnosis of concomitant thyroid nodules by US and US-FNAB were compared with the histopathological findings. Of the 109 patients, 19 (17.4%) had malignant thyroid nodules, 26 (23.9%) had benign thyroid nodules alone, and 12 (11.0%) had diffuse goiter. The sensitivity, specificity, and accuracy of diagnosing 72 thyroid nodules were 91.3%, 91.8%, and 91.7% for US, 57.9%, 94.3%, and 81.5% for US-FNAB, and 95.7%, 91.8%, and 93.1% for combined US and US-FNAB, respectively. True positive/false negative ratio of US-FNAB diagnosis was significantly lower in nodules of 5-9 mm than nodules of 10 mm or more. Four unexpected thyroid cancers existed at a different site in 3 of the 39 patients with palpable thyroid disease. Five thyroid cancers were histopathologically confirmed in 5 (7.1%) of 70 patients without palpable thyroid disease. Eight (88.9%) of the 9 non-palpable thyroid cancers were accurately diagnosed by combined US and US-FNAB. Preoperative US is useful for evaluation of possible concomitant thyroid disease, especially for prediction of malignancy.

The incidentaloma of the thyroid

The incidentally detected thyroid nodule using sonography is described as incidentaloma; the most nodules have a diameter up to 1.5 cm. Sonography will detect thyroid nodules in more than 20% of the population in Germany. Epidemiological studies investigating the prevalence of malignancy in such incidentalomas are missing. The incidence of differentiated thyroid cancer is about 3 per 100,000 people and year. However, several monocentric studies have shown a prevalence of malignancy of up to 10% of the thyroid nodules in selected patients' group. The histology did notfound microcarcinomas only, but also small cancer with infiltration of the thyroid capsule, lymph node metastasis or multifocal spread. The studies were not designed for outcome measurement after early and incidental detection of small thyroid cancers. Hypoechogenity, ill defined borders, central hypervascularization or microcalcifications were used as combined criteria for risk stratification. The second method for risk stratification is scintigraphy and further tests are warranted for hypofunctioning nodule > or =1 cm. Additionally, the family history, patient's age <20 years, former radiation of the neck, and measurement of calcitonin should be regarded. Without such a risk stratification selection for fine needle aspiration is impossible. Fine needle aspiration of non-palpable incidentalomas led to non-representative or unequivocal cytological findings in up to 40%. Because better outcome of incidentally detected small thyroid carcinomas is not proved and because sonography, scintigraphy and fine needle aspiration remain imprecise regarding dignity of incidentalomas, fine needle aspiration is not the standard for small, non-palpable thyroid nodules. For management of incidentaloma, sonographically unsuspicious, scintigraphically indifferent (nodules > or =1 cm) and without any risk factors in patients' history, wait and see is justified when patient is informed about the problem.

Small carcinomas of the thyroid diagnosed by US-guided FNA

5595 Background: The introduction of highly sensitive imaging technique has made it possible to detect many nonpalpable nodules in the thyroid. Discovery of these lesions raises concern about their malignancy and some of them are found thyroid cancer. This study wants to review evidence about small carcinomas of the thyroid and provide recommendations for their evaluation and treatment. Methods: Four hundred one patients with thyroid cancer had initial treatment at Kyungpook National University Hospital from Jan. 2001 to Jun. 2003. Seventy-nine patients(19.7%) were nonpalpable thyroid cancer and diagnosed by preoperative FNA. Results: Median tumor size was 1.01cm. Seventy patients(88.6%) are female. Fifteen patients(19%) had multiple lesions. 64.5 percent of patients underwent near-total thyroidectomy. Radioiodine remnant ablation was performed in 25 patients(31.6%). 96 percent of dominant structure of the lesion was papillary carcinoma. Seventeen patients(21.5%) had nodal metastasis including five patien...

Small carcinomas of the thyroid diagnosed by US-guided FNA

5595 Background: The introduction of highly sensitive imaging technique has made it possible to detect many nonpalpable nodules in the thyroid. Discovery of these lesions raises concern about their malignancy and some of them are found thyroid cancer. This study wants to review evidence about small carcinomas of the thyroid and provide recommendations for their evaluation and treatment. Methods: Four hundred one patients with thyroid cancer had initial treatment at Kyungpook National University Hospital from Jan. 2001 to Jun. 2003. Seventy-nine patients(19.7%) were nonpalpable thyroid cancer and diagnosed by preoperative FNA. Results: Median tumor size was 1.01cm. Seventy patients(88.6%) are female. Fifteen patients(19%) had multiple lesions. 64.5 percent of patients underwent near-total thyroidectomy. Radioiodine remnant ablation was performed in 25 patients(31.6%). 96 percent of dominant structure of the lesion was papillary carcinoma. Seventeen patients(21.5%) had nodal metastasis including five patien...

Surgeon-Performed Ultrasound in the Management of Thyroid Malignancy

Surgeon-controlled real-time ultrasound (US) is a new adjunct in the management of patients with thyroid malignancy. The introduction of US as a routine evaluation tool has increased the recognition of nonpalpable thyroid cancers and cervical lymph node metastases. We report our experience and the change in management of patients with thyroid cancer due to the use of US. We reviewed the records of all patients undergoing neck operations for thyroid cancer since 2002. US was performed by a surgeon preoperatively in all patients and intraoperatively when non-palpable cervical lymph nodes were present. Suspicious nonpalpable thyroid nodules underwent US-guided fine-needle aspiration (FNA) for cytology. Seventy-two patients underwent operations for thyroid cancer. US influenced the management in 57 per cent (41/72) of patients. US was useful in 1) identification and guidance for the FNA of nonpalpable cancers in 28 per cent (20/72), 2) identification of nonpalpable nodules in the contralateral lobe in 38 per cent (27/72), 3) preoperative diagnosis of nonpalpable metastatic lymph nodes in 24 per cent (17/72), and intraoperative guidance for their excision. Surgeon-performed US changed and enhanced the pre- and intraoperative management in more than half the patients with thyroid cancer.

Nonpalpable thyroid carcinoma: clinical controversies on preoperative selection.

This article emphasizes some controversies concerning the preoperative selection of nonpalpable thyroid tumors. The prevalence of occult thyroid carcinoma in surgical series (1.8-10%) is not higher than in autopsy thyroid series (2.7-24%). The prevalence of occult thyroid carcinoma in thyroid glands examined in the same institution by ultrasound, for a clinical thyroid abnormality or for investigation of other neck structures without clinically evident or suspected thyroid disease, varies from 3% to 8% and is very similar independent of the fact that a thyroid abnormality is or is not the indication for ultrasonography. These data suggest that the presence of a thyroid disease is not a risk factor for harboring an occult thyroid carcinoma (except for C-cell hyperplasia in the rare case of MEN 2 syndromes). As it is not cost effective to examine all the nonpalpable lesions with fine-needle aspiration (FNA) guided by ultrasounds, it is necessary to define to which extent ultrasound is useful in selecting those lesions to be examined cytologically by FNA. The use of ultrasound to select these lesions is very controversial. Ultrasound-guided cytologic diagnosis of nonpalpable nodules is not as accurate as in the case of palpable nodules. Sampling of material adequate for cytologic analysis depends on the lesion size; it is 64% for a 0.7-cm lesion and it increases to 86.7% for a mean size of 1.1 cm. For the diagnosis of occult thyroid carcinomas (< or =1 cm), sensitivity is 35.8% and false-negative results are 49.3%. Nonpalpable nodules with a size of 1.5 cm represent an absolute indication to perform an ultrasound-guided FNA because this is the size limit for dividing thyroid nodules in probably innocuous or potentially dangerous categories and because the cytologic diagnosis of nodules of this size is sufficiently reliable. For the smaller incidentally discovered thyroid nodules following ultrasound, physicians should discuss with the patient whether and when to perform an ultrasound-guided FNA considering the patient's data (risk factors, age, health state, etc.), the natural history of a small thyroid carcinoma, as well as the accuracy of ultrasound and ultrasound-guided FNA in the specific institution.

Clinical relevance of non-palpable thyroid nodules as assessed by ultrasound-guided fine needle aspiration biopsy.

It is known from autopsy data that thyroid nodules are far more common than can be detected by palpation alone. With the wide use of modern non-invasive imaging many non-palpable thyroid nodules are discovered but the proper approach to these nodules is still debatable. In a retrospective study, we reviewed the data from 186 US-guided FNA biopsies (US-FNAB) performed between May 1995 and March 1997 at the Sapir Medical Center, Israel, a iodine-sufficient urban area. Sixty-one of the 186 US-FNAB of the thyroid were performed in non-palpable nodules. The mean size of these nodules was 2.4 +/- 1.0 cm (mean +/- SD) ranging from 1.1-5.5 cm. Description of the nodule consistency was available in 53 cases; 42/53 were solid and 11/53 were solid-cystic. FNAB was diagnostic in 46 patients and non-diagnostic in 15. Forty-three of the diagnostic cytology reports were benign, one revealed papillary carcinoma, one had suspicious findings and the third was suspicious for a follicular neoplasm. The last two patients were referred to surgery and a follicular adenoma was found in both. Among the 61 non-palpable thyroid nodules, only one was papillary carcinoma, a prevalence of 1.6%. The other two patients referred to surgery had benign lesions. We found a low prevalence of malignancy in relatively large non-palpable thyroid nodules.

Diagnosis of Occult Thyroid Carcinoma by Ultrasonography

The increased sensitivity of many imaging devices has increased the identification of asymptomatic nodules in the thyroid gland. In this study we investigated the actual incidence of nonpalpable thyroid nodules and occult carcinoma in women. Between January and June 2003, among the women who were scheduled to undergo breast ultrasonography, 697 without palpable thyroid nodules were screened for thyroid nodules. They were classified into four categories according to ultrasonographic findings: negative, benign, indeterminate and malignant. Ultrasound-guided fine-needle aspiration biopsy (FNAB) was carried out for all malignant lesions and for some of the benign and indeterminate ones. The nodule detection and malignancy rates were determined and the effectiveness of ultrasonography as a diagnostic tool was also investigated. Out of the 697 subjects, 246 (35.3%) were found to have thyroid nodules. The malignancy detection rate based on the FNAB results, including both suspicious and malignant groups, was 3.6% (25/697) for all subjects. In addition, 3.0% (21/697) of all the women were confirmed to have thyroid cancer by surgery. The sensitivity of sonographic classification was increased from 80% to 100% when the indeterminate class was added to the malignant one, although this decreased the specificity from 91.7% to 33.3%. In conclusion, high-resolution ultrasonography detected a high percentage of malignant nodules. Ultrasonography can augment its value by guiding FNAB, in addition to providing diagnostic images.

Risk of Malignancy in Nonpalpable Thyroid Nodules: Predictive Value of Ultrasound and Color-Doppler Features

The aim of the study was to correlate the sonographic [ultrasound (US)] and color-Doppler (CFD) findings with the results of US-guided fine needle aspiration biopsy (FNA) and of pathologic staging of resected carcinomas to establish: 1) the relative importance of US features as risk factors of malignancy; and 2) a cost-effective management of nonpalpable thyroid nodules. Four hundred ninety-four consecutive patients with nonpalpable thyroid nodules (8–15 mm) were evaluated by US, CFD, and US-FNA. Ninety-two patients with inadequate cytology were excluded from the study. All patients with suspicious or malignant cytology underwent surgery, whereas subjects with benign cytology had clinical and US control 6 months later. Thyroid malignancies were observed in 18 of 195 (9.2%) solitary thyroid nodules and in 13 of 207 (6.3%) multinodular goiters. Cancer prevalence was similar in nodules greater or smaller than 10 mm (9.1 vs. 7.0%). Extracapsular growth (pT4) was present in 35.5%, and nodal involvement in 19.4% of neoplastic lesions, with no significant differences between tumors greater or smaller than 10 mm. At US cancers presented a solid hypoechoic appearance in 87% of cases, irregular or blurred margins in 77.4%, an intranodular vascular pattern in 74.2%, and microcalcifications in 29.0%. Irregular margins (RR 16.83), intranodular vascular spots (RR 14.29), and microcalcifications (RR 4.97) were independent risk factors of malignancy. FNA performed on hypoechoic nodules with at least one risk factor was able to identify 87% of the cancers at the expence of cytological evaluation of 38.4% of nonpalpable lesions. The majority of nonpalpable thyroid tumors can be identified by cytological evaluation of lesions presenting hypoechoic appearance in conjunction with one independent risk factor. Due to the nonnegligible prevalence of extracapsular growth and nodal metastasis, US-FNA should be performed on all 8–15 mm hypoechoic nodules with irregular margins, intranodular vascular spots or microcalcifications. Nonpalpable lesions of the thyroid without risk factors should be followed by means of clinical and US evaluation.

Risk of malignancy in nonpalpable thyroid nodules: predictive value of ultrasound and color-Doppler features.

The aim of the study was to correlate the sonographic [ultrasound (US)] and color-Doppler (CFD) findings with the results of US-guided fine needle aspiration biopsy (FNA) and of pathologic staging of resected carcinomas to establish: 1) the relative importance of US features as risk factors of malignancy; and 2) a cost-effective management of nonpalpable thyroid nodules. Four hundred ninety-four consecutive patients with nonpalpable thyroid nodules (8-15 mm) were evaluated by US, CFD, and US-FNA. Ninety-two patients with inadequate cytology were excluded from the study. All patients with suspicious or malignant cytology underwent surgery, whereas subjects with benign cytology had clinical and US control 6 months later. Thyroid malignancies were observed in 18 of 195 (9.2%) solitary thyroid nodules and in 13 of 207 (6.3%) multinodular goiters. Cancer prevalence was similar in nodules greater or smaller than 10 mm (9.1 vs. 7.0%). Extracapsular growth (pT(4)) was present in 35.5%, and nodal involvement in 19.4% of neoplastic lesions, with no significant differences between tumors greater or smaller than 10 mm. At US cancers presented a solid hypoechoic appearance in 87% of cases, irregular or blurred margins in 77.4%, an intranodular vascular pattern in 74.2%, and microcalcifications in 29.0%. Irregular margins (RR 16.83), intranodular vascular spots (RR 14.29), and microcalcifications (RR 4.97) were independent risk factors of malignancy. FNA performed on hypoechoic nodules with at least one risk factor was able to identify 87% of the cancers at the expence of cytological evaluation of 38.4% of nonpalpable lesions. The majority of nonpalpable thyroid tumors can be identified by cytological evaluation of lesions presenting hypoechoic appearance in conjunction with one independent risk factor. Due to the nonnegligible prevalence of extracapsular growth and nodal metastasis, US-FNA should be performed on all 8-15 mm hypoechoic nodules with irregular margins, intranodular vascular spots or microcalcifications. Nonpalpable lesions of the thyroid without risk factors should be followed by means of clinical and US evaluation.

Nonpalpable Thyroid Nodules—Managing an Epidemic

Nonpalpable Thyroid Nodules—Managing an Epidemic

New Sonographic Criteria for Recommending Fine-Needle Aspiration Biopsy of Nonpalpable Solid Nodules of the Thyroid

The purpose of our study was to provide new sonographic criteria for fine-needle aspiration biopsy of nonpalpable solid thyroid nodules. Sonographic scans of 155 nonpalpable thyroid nodules in 132 patients were prospectively classified as having positive or negative findings. Sonographic findings that suggested malignancy included microcalcifications, an irregular or microlobulated margin, marked hypoechogenicity, and a shape that was more tall than it was wide. If even one of these sonographic features was present, the nodule was classified as positive (malignant). If a nodule had none of the features described, it was classified as negative (benign). The final diagnosis of a lesion as benign (n = 106) or malignant (n = 49) was confirmed by fine-needle aspiration biopsy and follow-up (>6 months) in 83 benign nodules, by fine-needle aspiration biopsy and surgery in 44 malignant and 15 benign lesions, and by surgery alone in five malignant and eight benign lesions. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were calculated on the basis of our proposed classification method. Of 82 lesions classified as positive, 46 were malignant. Of 73 lesions classified as negative, three were malignant. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy based on our sonographic classification method were 93.8%, 66%, 56.1%, 95.9%, and 74.8%, respectively. Considering the high level of sensitivity of our proposed sonographic classification, fine-needle aspiration biopsy should be performed on thyroid nodules classified as positive, regardless of palpability.

Evaluation of Innovative Skin-Marking Technique Performed Before Thyroid Ultrasound-Guided Fine-Needle Aspiration Biopsies

To introduce an innovative skin-marking technique performed before ultrasound-guided fine-needle aspiration biopsy (US-FNAB) of the thyroid. We studied 248 patients with thyroid nodules, who were classified on the basis of physical examination into two groups-those with palpable nodules (N = 127) and those with nonpalpable or difficult-to-palpate nodules (N = 121). Each group was further subdivided according to the size of the thyroid nodule (< or = 15 mm versus >15 mm). Before US-FNAB, we performed the skin-marking technique with the aid of a catheter, a permanent marker, and ultrasound guidance. An established point for needle entry was indicated on the skin. The chi-square test was used to compare results between the groups of patients. The proportions of adequate and insufficient biopsy material in the overall group of patients were 88.7% and 11.3%, respectively. When the patients were stratified by palpable and nonpalpable thyroid nodules, biopsy specimens were adequate in 89.8% and insufficient in 10.2% of those with palpable nodules, whereas the corresponding proportions for those with nonpalpable nodules were 87.6% and 12.4%, respectively. No statistically significant differences were noted between the two groups. Comparisons between patients with thyroid nodules >15 mm in their largest diameter versus those with nodules < or =15 mm also showed no statistically significant differences in terms of insufficient biopsy material. Our technique creates a marking on the skin that leads directly to the thyroid nodule and facilitates the acquisition of adequate cytologic material. This is particularly relevant when small transducers are not available or when the physician needs reassurance about the accuracy of the thyroid biopsy site.

Non-palpable thyroid nodules in a borderline iodine-sufficient area: Detection by ultrasonography and follow-up

Thyroid ultrasonography was performed in 482 subjects, free of known thyroid disease and living in a borderline iodine-sufficient urban area, to assess the prevalence of non-palpable thyroid nodules and evaluation their evolute during a 3-yr follow-up. The mean (+/-SD) thyroid volume in the whole study group was 10.9+/-3.7 ml and was higher in males (12.9+/-3.6 ml) than in females (9.2+/-2.9 ml) (p<0.0001). Thyroid volume was correlated with body surface, height and weight, while no correlation was present with lean and fat body mass. Goiter was found in 5/256 females and in 13/226 males. Thyroid nodules were found in 27/482 subjects (18 females, 9 males). Single nodules were found in 17/464 subjects (3.66%) with a thyroid gland of normal volume and in 4/18 subjects (22.2%) with goiter (chi2=10.21; p=0.001). Multiple nodules were found in 3/464 subjects (0.6%) with a thyroid of normal volume and in 3/18 (16.6%) subjects with goiter (chi2=24.31; p<0.0001). The prevalence of thyroid nodules was significantly higher in females >35 yr than in those <34 yr (chi2=7.47; p=0.0062). A significant increase (>30%) of nodular volume was found in 5 subjects, while an increased number of nodules was found in 8. In conclusion, thyroid ultrasonography reveals the presence of thyroid nodules in a significant proportion of apparently thyroid disease-free subjects living in a borderline iodine-sufficient urban area. Incidentally discovered thyroid nodules are associated with goiter and are likely to progress in volume and number.

Subclinical Thyroid Disease

Subclinical Thyroid Disease

Indications and Limits of Ultrasound-Guided Cytology in the Management of Nonpalpable Thyroid Nodules

Indications and Limits of Ultrasound-Guided Cytology in the Management of Nonpalpable Thyroid Nodules

Indications and limits of ultrasound-guided cytology in the management of nonpalpable thyroid nodules.

Although ultrasound (US)-guided fine needle aspiration biopsy (FNAB) is widely prescribed in nonpalpable thyroid nodules, the goal of this study was to define precisely the indications and limits of US-FNAB in a series of 450 nonpalpable nodules. Among 94 surgically controlled cases, 20 (8 infracentimetric and 12 centimetric or supracentimetric) carcinomas were diagnosed. The diagnosis of malignancy was successfully made by US-FNAB in 16 of 20 carcinomas, 3 were missed because of insufficient cytological material, and 1 was misdiagnosed. US-FNAB sensitivity and specificity were 94% and 63%, respectively. A logistic model indicated that nodule size (P < 0.6) was not associated with histological diagnosis, but that solid hypoechoic features were more likely to be malignant (P < 0.0003), with US sensitivity and specificity for malignancy of 80% and 70%, respectively. Logistic regression indicated that adequate cytological material significantly increased with nodule size (P < 0.0001). This result outlined the limits of US-FNAB in small nodules. Hence, indication of US-FNAB appears judicious in centimetric or supracentimetric nodules or in solid and hypoechoic ones. Such a management would allow the discovery of 15 of 20 carcinomas and would avoid 16% of unnecessary biopsies.

The role of ultrasonography-guided fine-needle aspiration biopsy in the management of nonpalpable and palpable thyroid nodules.

The introduction of highly sensitive imaging techniques has made it possible to detect many nonpalpable thyroid nodules (non-PTN). We investigated the value of ultrasound-guided fine-needle aspiration biopsy (US-guided FNAB) as a diagnostic tool in the management of non-PTN as well as palpable thyroid nodules (PTN) that were considered difficult to aspirate without guidance. US-guided FNAB was performed on a total of 119 nodules (71 palpable and 48 nonpalpable) from 119 patients between 1992 and 1996. All available clinical and follow-up data were reviewed. Surgical follow-up was available in 24 cases. The patients included 100 females and 19 males ranging in age from 9 to 81 years (average, 51 years). FNA diagnoses (PTN versus non-PTN) included papillary carcinoma (12.7% [9/71] versus 4.2% [2/48], follicular neoplasm (16.9% [12/71] versus 0%), medullary carcinoma (1.4% [1/71] versus 0%), atypical cytology (5.6% [4/71] versus 2.1% [1/48], non-neoplastic thyroid (63.4% [45/71] versus 85.4% [41/48]) and unsatisfactory (0% versus 8.3% [4/48]). In 2 cases of occult papillary carcinoma, risk factors included radiation exposure (1 case) and a newly developed nodule during follow-up for hypothyroidism (1 case). Subsequent surgical follow-up (24 cases) confirmed the FNA findings, except for a case of Hürthle cell adenoma and 1 of Hashimoto's thyroiditis diagnosed as papillary carcinoma and follicular neoplasm, respectively. US-guided FNAB in most non-PTN are diagnosed as benign. For most patients with non-PTN and without any high-risk factors, a conservative approach such as clinical follow-up may be a more cost effective and logical approach. In contrast, US-guided FNAB is more useful in diagnosing biologically significant lesions in PTN that may be difficult to aspirate without guidance.

Thyroid incidentalomas: management approaches to nonpalpable nodules discovered incidentally on thyroid imaging.

The introduction of highly sensitive imaging techniques has made it possible to detect many non-palpable nodules, or "incidentalomas," in the thyroid. Discovery of these lesions raises concerns about their malignancy, but the optimal strategy for managing these lesions has not been clearly established. To review evidence about incidentalomas, including prevalence and risk for malignancy, and to provide recommendations for their evaluation and treatment. Literature searches for relevant articles published in the past 15 years in major English-language medical journals, review of selected articles published before this period, and reviews of bibliographies in text-books. Three studies on autopsy findings, 11 studies on ultrasonographic findings, and other reports on nonpalpable thyroid nodules were included. Data on the prevalence of nodules on autopsy and in ultrasonographic series, palpation compared with ultrasonography, the risk for malignancy in nodules found in irradiated glands, the natural history of thyroid nodules, and the prevalence of occult cancer were collated and reviewed. Prevalence of thyroid incidentalomas estimated from autopsy studies ranges from 30% to 60%. Studies comparing clinical palpation with thyroid imaging show a prevalence of 13% to 50%. Prospective studies of randomly selected patients have reported a prevalence of 19% to 67%. The risk for malignancy in asymptomatic nodules found in nonirradiated glands is 0.45% to 13% (mean +/- SD, 3.9% +/- 4.1%). High-resolution ultrasonography is sensitive and capable of detecting many small, nonpalpable thyroid nodules. Most of these lesions are benign. For most patients with nonpalpable nodules that are incidentally detected by thyroid imaging, simple follow-up neck palpation is sufficient.