Benign looking thyroid nodules have different lymph node metastatic risk and histologic types according to the ultrasonographic size

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SUN 303-321-Cancer in Endocrine Tissues
Bench to Bedside
Sunday, June 16, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SUN-306
Young Ki Lee*1, Dong Yeob Shin1, Kwang Joon Kim1, Kyeong Hye Park1, Sena Hwang1, Young Duk Song2 and Eun Jig Lee1
1Yonsei University College of Medicine, Seoul, South Korea, 2National Health Insurance Corporation Ilsan Hospital, Gyeonggi-do, South Korea
Objective

Nowadays, a decision on whether or not to perform a fine needle aspiration (FNA) on thyroid nodules is more dependent on suspicious ultrasonographic features than on the tumor size itself. We aimed to investigate if lymph node metastasis (LNM) risk differed by tumor size of thyroid cancers with benign looking ultrasonographic features that might had been neglected with the FNA policy mentioned above.

Methods

We retrospectively analyzed a total of 360 patients with thyroid cancers who, on thyroid ultrasonography (US), were reported to have benign looking nodules (lack of suspicious features: marked hypoechogenicity, irregular or taller than wide shape, speculated margins, and microcalcifications) and who underwent thyroidectomy with appropriate lymph node dissection including prophylactic central compartment neck dissection due to suspicious FNA cytology. The patients were classified based on tumor size observed on US (≤ or > 1 cm). The clinicopathogic parameters, including age, sex, histology types, and tumor size on final pathology, the presence of extrathyroidal extension (ETE), LNM, and multiplicity were compared between the two groups. A multivariate analysis was performed to discover the independent factors predicting the presence of LMN.

Results

The group with nodules greater than 1 cm in diameter on US (n=157) demonstrated larger tumor size on histology (17.9 ± 14.5 mm vs. 5.6 ± 2.4 mm, p < 0.001), lower frequency of classical papillary thyroid carcinoma (PTC) (58.6% vs. 87.2%, p < 0.001), and higher frequency of follicular variant PTC and follicular thyroid carcinoma (19.7% and 17.8% vs. 9.4% and 1.5%, respectively, p < 0.01). Otherwise, the parameters were not significantly different between the two groups. However, on analyzing 269 patients with pathologically confirmed classical PTC, the group with larger nodule on US were found to have a significantly increased risk of LNM (28.3% vs. 14.7%, p = 0.007). In addition to presence of classical PTC and ETE, the tumor size on US (odds ratio, 2.10 (95% CI, 1.13-3.90)) was an independent predictive factor of LNM after adjusting for age, sex, TSH level, and multiplicity.

Conclusions

Thyroid nodules larger than 1 cm in diameter that presents with benign features on US are more likely to be non-classical PTC than those with smaller diameter; if classical PTC, the larger nodules also have increased risk of LNM. These cases require a more aggressive approach to FNA, as well as a close follow up.

Nothing to Disclose: YKL, DYS, KJK, KHP, SH, YDS, EJL

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm