Needle biopsy in the assessment and management of hypofunctioning thyroid nodules

Validation of a five-tier cytodiagnostic system for thyroid fine needle aspiration biopsies using cytohistologic correlation

OBJECTIVE

Approximately 70-80% of thyroid fine needle aspiration biopsies (FNAB) can distinguish benign from malignant thyroid nodules. However, much interpretive diagnostic difficulty arises with the remaining 20-30% of cases. These problematic thyroid aspirations have been placed in various diagnostic categories, which collectively have led to confusion and a negative impact on the clinical management of patients with thyroid nodules. We present our experience using a five-tier system, including the diagnostic terminology: benign, indeterminate, suspicious, malignant, and unsatisfactory.

DESIGN

Thyroid FNABs were diagnosed using a five-tier system from 200 consecutive patients and the subsequent surgical excisions were correlated.

MAIN OUTCOME

Overall, there was an excellent association between the five diagnostic categories and predicting benign versus neoplastic thyroid nodules (LR = 96.06, X(2) = 76.49, and phi = 0.618, df = 4, p < 0.0001). A negative cytologic diagnosis carries a negative predictive value of 92%, while an indeterminate, suspicious, and malignant cytologic diagnosis carries a positive predictive value of 50, 71, and 100% respectively. The estimated sensitivity for an indeterminate, suspicious, or malignant cytologic diagnosis varied from 70 to 89%, while the specificity increased from 57 to 92 to 100%, respectively.

CONCLUSIONS

The data presented shows that the five diagnostic categories of thyroid FNAB are excellent at distinguishing benign from neoplastic thyroid nodules. Both the indeterminate and suspicious categories, while not statistically different from each other in predicting benign from neoplasia, are statistically different from obviously benign and obviously malignant categories. These results support the need for an indeterminate and/or suspicious category.

The value of onsite adequacy assessment of thyroid fine-needle aspirations is a function of operator experience

BACKGROUND

Cytotechnologists and pathologists often perform onsite evaluations of thyroid fine-needle aspirations (FNAs) to provide immediate feedback regarding whether adequate material has been obtained for cytologic diagnosis. The current study was designed to determine whether onsite adequacy assessment results in a significant decrease in nondiagnostic specimens between ultrasound (US)-guided FNAs of the thyroid and those performed by palpation alone.

METHODS

A search was performed to identify in-house thyroid FNAs performed between January 1, 2000 and December 31, 2003 that were obtained under US guidance or by palpation only. It was then recorded whether an onsite adequacy assessment was performed. The submitting physician and final diagnosis also were recorded for each case. Contingency tables were constructed and evaluated using chi-square analysis.

RESULTS

Of 1502 in-house thyroid FNAs included in the current study, 981 (65.3%) were performed under US guidance and 521 (34.7%) were performed with palpation alone. Onsite adequacy assessment of the aspirated material was performed in 323 cases (21.5%), whereas 1179 cases (78.5%) were performed without onsite evaluation. Of the 418 palpation-guided FNAs that were performed without adequacy assessment, 70 (16.7%) were reported to be nondiagnostic, whereas of the 103 palpation-guided FNAs with immediate evaluation, only 7 (6.8%) were determined to be inadequate for diagnosis. This difference was statistically significant (P < 0.025). Of 761 US-guided FNAs without immediate adequacy assessment, 54 (7.1%) were nondiagnostic, which was not statistically different from the nondiagnostic rate of 4.5% (10 of 220 cases) for US-guided FNAs with onsite evaluation. However, when these US-guided FNAs were divided further into 2 groups based on the experience of the radiologist performing the FNA, the nondiagnostic rate in the group of experienced radiologists was only 5.4% (or 32 of 592 US-guided FNAs), even though onsite evaluation was not performed. Among radiologists with less experience, adequacy assessment significantly reduced the nondiagnostic rate from 13.0% (22 of 169 FNAs without adequacy assessment) to 4.5% (10 of 220 FNAs with adequacy assessment) (P < 0.01).

CONCLUSIONS

The results of the current study demonstrate that onsite adequacy assessment of thyroid FNAs significantly reduces the number of nondiagnostic aspirates. However, the benefit of onsite evaluation, at least for US-guided FNAs, depends on the experience of the radiologist. In the current study, experienced radiologists with a relatively low nondiagnostic rate did not benefit from onsite adequacy assessment. This finding confirms the importance of experience in the performance of FNA, but suggests that onsite adequacy assessment may assist the less experienced operator.

Fine-Needle Aspiration of Thyroid Nodules: Past, Present, and Future

OBJECTIVE

To present a review of the traditional and more recent techniques and applications of thyroid fine-needle aspiration biopsy.

METHODS

We describe the cytologic features and differential diagnoses of various thyroid lesions, outline recommendations for diagnostic categories, and discuss new techniques that have shown some promise in the diagnosis of thyroid nodule fine-needle aspiration specimens.

RESULTS

Fine-needle aspiration biopsy of the thyroid has proved to be an excellent diagnostic tool in the initial management of thyroid nodules. Numerous studies have shown its high sensitivity and specificity in diagnosing malignant tumors of the thyroid, especially papillary thyroid carcinoma. As with other diagnostic tests, however, its effectiveness is highly dependent on the expertise of the operator performing the procedure and the adequacy of the specimen for interpretation of the cytomorphologic features. On-site evaluation of thyroid specimens promotes adequate specimen sampling and reduces the incidence of nondiagnostic specimens. Diagnostic reports on thyroid fine-needle aspiration should include patient demographics and pertinent clinical history, site and size of the thyroid nodule, mode of aspiration, number of needle passes, assessment of specimen adequacy, diagnosis, and recommendations. Although immunohistochemical and molecular markers have received considerable attention recently, additional studies are needed before they can be used to separate benign from malignant follicular thyroid lesions.

CONCLUSION

Overall, fine-needle aspiration biopsy of thyroid nodules has proved to be sensitive, specific, and well accepted by patients because of minimal discomfort and complications.

Treatment of cystic lesions of the thyroid by ethanol instillation

We analyzed the results of ethanol sclerotherapy in 61 patients with cystic thyroid lesions which recurred after aspiration. Cytologic study showed all of the lesions to be benign. The patients were followed clinically and ultrasonically 1 month and 6 or more months after treatment. If the cystic lesions recurred, repeated treatment was offered. During the follow-up, 36 (59.0%) patients experienced no recurrence after the initial treatment and 5 (8.2%) patients received treatments 2 or more additional times. In 44 (72.1%) of the 61 patients, the cystic lesion almost disappeared or decreased in size, but in 17 (27.9%) patients it did not decrease. Four patients underwent surgery after the ethanol sclerotherapy. Although no severe complications were observed, there were complaints of slight pain in 12 patients, severe pain in 1 patient, and a drunken feeling in 1 patient. We consider instillation of ethanol into recurrent cystic lesions of the thyroid to be a simple, safe, economical, and effective treatment.

Fine-needle aspiration biopsy of cold thyroid nodules

This study analyzes the results of fine-needle aspiration biopsy (FNAB) of hypofunctioning thyroid nodules performed by one physician. There were 68 patients (age range, 20 to 73 years) with 83 aspirations; 30 were interpreted as positive for neoplasm (adenoma or carcinoma), 43 were negative, and ten (12%) were technically unsatisfactory. Thyroidectomy was performed on 25 patients who had positive aspirates. Subsequent morphologic study showed that 13 patients had carcinomas, ten had adenomas, and two had adenomatoid nodules (false-positive rate of FNAB for neoplasms was 8%). One of three thyroidectomy patients with negative preoperative aspirates had a carcinoma and two had adenomas (estimated minimal false-negative rate of FNAB was 9%). Nineteen patients who underwent thyroidectomies had dynamic radioisotopic thyroid angiography. There was no correlation between the pattern of vascularity and the type of neoplasm. Ultrasound (US) study was performed on 17 patients. Both adenoma and carcinoma can be solid or partially cystic. Although approximately 33% of the nodules initially diagnosed by FNAB as follicular or papillary neoplasms had different interpretations on subsequent examination of thyroidectomy specimens, 93% of the patients selected to be operated on had either adenoma or carcinoma. Thus, in this series, FNAB of cold thyroid nodules gave more useful diagnostic information than nodule size, dynamic radioisotopic scan, or US studies.

Fine needle aspiration biopsy in diagnosis of metastases to thyroid gland

Three cases of metastasis to the thyroid gland are reported, in each of which fine needle aspiration biopsy confirmed the diagnosis and obviated the need for surgery. Fine needle aspiration biopsy is able to confirm suspected intrathyroid metastasis and can be performed as an outpatient or bedside procedure.