Reply:
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* E.M. Genden

The American Thyroid Association guidelines for the management of patients with thyroid nodules1 outlines the role of sonography and fine-needle aspiration for the evaluation of thyroid nodules. Our work and the work of others2(#ref-3)–4 suggest that fluorodeoxyglucose–positron-emission tomography (FDG-PET) positivity is associated with a significant risk of malignancy, not unlike the cytologic reading of “indeterminate cytology,” which, according to the task force (R9, recommendation B), states that a “lobectomy or total thyroidectomy should be considered.”1 We support the work of the American Thyroid Association and believe that FDG-PET positivity simply represents an adjunct to sonography and cytology for the risk assessment of a patient with a thyroid nodule. We do not advocate thyroidectomy for patients with benign cytology and retract any implication of such; however, we do inform patients of the data on FDG-PET positivity—after all, the false-negative rate for fine-needle aspiration of thyroid nodules is higher than the false-positive rate. The American Thyroid Association recommends that a lobectomy or total thyroidectomy be considered for indeterminate cytology, which is associated with a 5%–10% risk of malignancy. Do we feel comfortable withholding surgical intervention when FDG-PET positivity is associated with a 25%–50% risk of malignancy?

## References

1.  1. Cooper DS, Doherty GM, Haugen BR, et al. Management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid 2006;16:109–42 
    
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2.  2. Choi JY, Lee KS, Kim HJ, et al. Focal thyroid lesions incidentally identified by integrated 18F-FDG PET/CT: clinical significance and improved characterization. J Nucl Med 2006;47:609–15 
    
    [Abstract/FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Njoiam51bWVkIjtzOjU6InJlc2lkIjtzOjg6IjQ3LzQvNjA5IjtzOjQ6ImF0b20iO3M6MTk6Ii9ham5yLzMxLzIvRTMxLmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ==) 

3.  3. Kang KW, Kim SK, Kang HS, et al. Prevalence and risk of cancer of focal thyroid incidentaloma identified by 18F-fluorodeoxyglucose positron emission tomography for metastasis evaluation and cancer screening in healthy subjects. J Clin Endocrinol Metab 2003;88:4100–04 
    
    [CrossRef](http://www.ajnr.org/lookup/external-ref?access_num=10.1210/jc.2003-030465&link_type=DOI) 
    
    [PubMed](http://www.ajnr.org/lookup/external-ref?access_num=12970270&link_type=MED&atom=%2Fajnr%2F31%2F2%2FE31.atom) 
    
    [Web of Science](http://www.ajnr.org/lookup/external-ref?access_num=000185258700012&link_type=ISI) 

4.  4. Chen YK, Ding HJ, Chen KT, et al. Prevalence and risk of cancer of focal thyroid incidentaloma identified by 18F-fluorodeoxyglucose positron emission tomography for cancer screening in healthy subjects. Anticancer Res 2005;25:1421–6 
    
    [Abstract/FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTA6ImFudGljYW5yZXMiO3M6NToicmVzaWQiO3M6MTA6IjI1LzJCLzE0MjEiO3M6NDoiYXRvbSI7czoxOToiL2FqbnIvMzEvMi9FMzEuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9) 

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