Incidental Thyroid Nodule: OK, Now What?

Gordon H. Sun, MD, MS

Disclosures

December 13, 2016

Evaluating the Thyroid Incidentaloma

Dr Terris suggested that "overdetection leading to overtreatment" might be a more accurate description of the thyroid cancer workup process than the more generic term "overdiagnosis," which might suggest an inappropriately high false-positive rate of thyroid cancer diagnosis. Thyroid FNA is considered to be a very accurate and low-risk procedure, with 83% sensitivity, 92% specificity, 5% false-positive rate, and 5% false-negative rate.[13] FNA remains the gold standard of thyroid nodule evaluation after ultrasound. According to Dr Terris, improved diagnostic capabilities instead may be identifying a "subclinical reservoir of thyroid disease that may never be biologically relevant."

FNA remains the gold standard of thyroid nodule evaluation after ultrasound.

About 7%-15% of all thyroid nodules are cancerous, although the estimated risk for cancer varies widely on the basis of the six diagnostic categories outlined by the Bethesda System for Reporting Thyroid Cytopathology.[14] The American Thyroid Association (ATA) guidelines do not recommend surgery for benign nodules. However, FLUS and AUS are a point of contention. If molecular testing or repeat FNA is not performed or is inconclusive, the ATA guidelines recommend either diagnostic surgical excision or continued surveillance for FLUS/AUS findings.

What's in a Name?

Parallel to the debate about overdetection of thyroid disease has been a widespread effort to better understand and categorize thyroid lesions that pose minimal risk to patient health and survival. The follicular variant of papillary thyroid carcinoma (FVPTC) is one of several possible outcomes of a FLUS/AUS result on FNA, and the fourfold increase in FVPTC incidence over the past three decades may be attributable in part to overdetection of thyroid neoplasms and subsequent surgical intervention.[15]

In an August 2016 study, Nikiforov and colleagues[16] from an Endocrine Pathology Society working group retrospectively reviewed 210 cases of encapsulated FVPTC (EFVPTC) submitted from 13 international institutions, differentiating them into two groups on the basis of the presence of absence of invasive features. Of the 109 patients with noninvasive features, none had recurrence of disease after a median follow-up of 13 years, regardless of the extent of surgery. The authors subsequently recommended that this noninvasive form of EFVPTC be renamed "noninvasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP)—specifically eliminating any mention of cancer. The new nomenclature is expected to affect about 45,000 new patients worldwide annually.[16]

Dr Louise Davies, associate professor of surgery-otolaryngology with Dartmouth College in the White River Junction Vermont VA Outcomes Group, likened the issue to the suggested change in terminology of ductal carcinoma in situ (DCIS), a noninvasive form of breast cancer. That debate crystallized around a 2013 commentary by the National Cancer Institute proposing that premalignant conditions, such as DCIS, should be renamed without the word "cancer," using such terms as "IDLE (indolent lesions of epithelial origin) conditions."[17]

Several questions will need to be answered as healthcare providers and patients become more aware of this paradigm shift. Likhterov and colleagues,[18] as well as the New York Times, have commented that the removal of the burden of a cancer diagnosis alone will have a substantial financial, psychological, and physical impact.

Next, how the NIFTP diagnosis will affect risk stratification in the widely used Bethesda classification scheme is unclear, although a study by Faquin and colleagues[19] suggested that the cancer risk for all six categories will decrease, with the decline most pronounced in samples of indeterminate cytology. Some authors have noted that the NIFTP reclassification will affect the accuracy of thyroid FNA molecular testing in predicting malignancy.[15.20] Finally, diagnosing NIFTP requires assessment of tumor invasion, which may be difficult to distinguish from invasive EFVPTC preoperatively.[21]

Even though some authors have begun suggesting that preoperative ultrasound-guided FNA[22] or core needle biopsy[23] may be sufficient to distinguish NIFTP from more sinister pathology, thyroid lobectomy will probably remain the standard of care for confirmation.[14] Therapy for patients with NIFTP may still be less extensive, owing to eliminating the need for completion thyroidectomy and radioiodine ablation, as well as their associated complications and costs.

Case Continued: Managing FLUS/AUS

After receiving the FNA results, the patient was referred to an otolaryngologist for surgical counseling. Although the surgeon provided a compelling case for diagnostic thyroid lobectomy, the patient had a fear of undergoing anesthesia and asked whether it would be reasonable to "watch" the nodule and intervene only if it started causing symptoms. The surgeon was initially hesitant, but after further discussion, the patient was adamant that he did not want to have surgery at that time. The otolaryngologist promised to contact colleagues at a nearby tertiary care hospital about nonsurgical options.

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