Progress in the preoperative diagnosis of thyroid nodules: managing uncertainties and the ultimate role for molecular investigation

Thyroid nodules; interpretation and importance of fine-needle aspiration (FNA) for the clinician - practical considerations

Thyroid nodules are very common lesions. Despite that the great majority is benign, in a significant percentage of them there is an underlying malignancy. Malignant thyroid nodules should be managed surgically, while the more common benign thyroid nodules may be managed conservatively. A systemic and careful diagnostic evaluation is needed to recognize nodules (overtly malignant or with malignant potential), and to avoid unnecessary surgery in a large percentage of patients with benign disease. Fine-needle aspiration (FNA) has a central role in the diagnostic investigation of the patient with thyroid nodules. FNA is a safe, useful, and cost-effective procedure. To increase accuracy, FNA can be performed under ultrasonographic guidance (if needed). Its results may be particularly helpful in determining the indication for surgery. In contrast, the role of FNA in selecting the extent of surgery is limited today. This is due to the fact that during the last decade there is a clear trend toward radical surgical management of thyroid nodular disease (both benign and malignant) by total/near-total thyroidectomy.

Fine-needle aspiration biopsies in the management of indeterminate follicular and Hurthle cell thyroid lesions

Objectives: To determine the value of fine-needle aspiration biopsies (FNABs) of the thyroid and stratify the risk of malignancy within the indeterminate FNAB diagnostic category at our institution.

Study design: Case series with chart review of preoperative FNABs of consecutive patients who underwent total thyroidectomy between 2005 and 2007.

Subjects and Methods: A total of 115 cases were reviewed, and FNABs were categorized into four groups: benign, positive or suspicious for malignancy, indeterminate (follicular or Hurthle cell lesions), and nondiagnostic. Cytohistologic correlation was then established.

Results: The accuracy of FNAB in detecting thyroid malignancy was 88 percent with false-negative and false-positive rates of 13 percent and 7 percent, respectively. Overall, 52 percent of the indeterminate cases were carcinomas (48 percent of follicular lesions and 62 percent of Hurthle cell lesions). In the presence of cytologic atypia, the rate of malignancy increased to 75 percent and 83 percent for the follicular and Hurthle cell lesions, respectively.

Conclusions: FNAB is an accurate and helpful method for the evaluation of thyroid nodules with results directly correlating with management. Surgery should be considered for FNABs categorized as indeterminate, especially in the presence of cytologic atypia. Because of the high false-negative rate, benign FNABs require close follow-up with ultrasound examination and periodic biopsies.

Differentiating alternative splice variant patterns of human telomerase reverse transcriptase in thyroid neoplasms

BACKGROUND

Although fine-needle aspiration (FNA) biopsy of thyroid nodules is very sensitive in detecting thyroid malignancy, it remains ambiguous in 20-30% of cases. Current biomarkers for thyroid cancer lack either the sensitivity or specificity to substantially address this clinical problem. The aim of this study was to investigate the gene expression patterns of human telomerase reverse transcriptase (hTERT) alternative splice variants in benign and malignant thyroid tumors in an attempt to find a more reliable biomarker in the differential diagnosis of thyroid nodules.

METHODS

One hundred and thirty-three thyroid tumors from eight histopathological tumor types were collected from patients undergoing thyroid surgery at Johns Hopkins Hospital. Gene expression patterns of hTERT alternative splice variants were investigated in the tumors by nested reverse transcriptase-PCR. Telomerase enzyme activity was evaluated in a subset of 16 samples associated with the different hTERT patterns. Association of c-myc expression and hTERT patterns was also examined.

RESULTS

Malignant thyroid tumors exhibited a greater proportion of the active full-length hTERT transcript (0.57 +/- 0.15) than inactive splice variants, alpha(-) (0.13 +/- 0.02), or beta(-)/alpha(-)beta(-) deletion transcripts (0.30 +/- 0.11; p < 0.001). The opposite was observed in benign tumors, which exhibited greater proportions of beta(-)/alpha(-)beta(-) deletion transcripts (0.64 +/- 0.08) than either the full-length (0.19 +/- 0.06) or alpha(-) deletion transcripts (0.17 +/- 0.02; p < 0.001). Similar results were observed among a diagnostically challenging subset of 50 thyroid tumors that were suspicious for malignancy on FNA. Further, increased telomerase enzymatic activity was only associated with expression of the full-length hTERT isoform. In contrast, c-myc expression, which has been implicated in hTERT regulation, correlated with overall hTERT transcription without specificity for expression of the full-length isoform.

CONCLUSIONS

These differences in gene expression patterns of hTERT alternative splice variants may provide a useful adjunct to FNA diagnosis of suspicious thyroid tumors.

Thyroid fine needle aspiration: how to improve clinicians' confidence and performance with the technique

Studies from single institutions report an acceptable accuracy rate for thyroid fine needle aspiration (FNA). However, FNA accuracy is much lower in many other centers in Europe and the USA and large multicenter studies indicate that the clinicians' confidence in the FNA technique remains low. One explanation for this is that there is an excess of inadequate and indeterminate findings for a follicular nodule at FNA cytology. In a University Hospital with large and qualified experience on thyroid nodule diagnosis, a review of 320 slides with an FNA diagnosis of indeterminate follicular nodule from different minor Italian Hospitals led to a different diagnosis in 61%. Since ancillary thyroid imaging may be overutilized and only a few authors report a proportion of excised nodules lower than 10%, we suspect that use of the FNA procedure is suboptimal. Several techniques are reported to improve the performance of thyroid FNA. Among these are tumor markers and large needle aspiration biopsy (LNAB). Immunodetection of the tumor marker galectin-3 has been evaluated by large multinational studies. Analysis of LNAB specimens reduces the number of inadequate FNA findings, improves the diagnostic determination of indeterminate follicular FNA findings and represents a better substrate for the determination of galectin-3. Therefore, we propose that clinical practice guidelines reflect these adjuvant techniques to thyroid FNA in order to improve selection criteria for thyroid nodule surgery.