Thyroid nodules ≤5 mm on ultrasonography: are they “leave me alone” lesions?

Abstract

The incidence of small thyroid malignancy has increased. However, there is no evidence-based guideline for managing thyroid nodules ≤ 5 mm on ultrasonography (US). We evaluated how to manage thyroid nodules ≤ 5 mm. Thyroid nodules ≤ 5 mm in size on US that had undergone surgery and US-guided fine-needle aspiration were eligible. A total of 3,117 thyroid nodules in 3,012 patients were included. The size changes of malignant and benign nodules during follow-up were evaluated. Thyroid malignancies were classified according to follow-up and surgery time within and after 12 months. Clinico-pathological characteristics were compared. Of 3,117 nodules, 1,639 nodules in 1,619 patients were benign and 1,478 in 1,427 were malignant. Only 5.8 and 1.2 % of malignant nodules and 6.8 and 4.2 % of benign nodules increased in size when a 2-mm and 3-mm change on US were referenced. Of 1,079 patients with an index malignancy ≤ 5 mm, extrathyroidal extension, lymph node metastasis, recurrence, and mortality were not significantly different between patients with and without follow-up and between patients with surgery within 12 months and after 12 months. None of the patients who underwent surgery had distant metastasis and none died of thyroid malignancy. In thyroid nodules ≤ 5 mm found on US, US-FNA could be recommended in cases of increased size during US follow-up if lateral LNM was not found because a delay in surgery did not impact cancer recurrence and mortality.

Sonographic Detection of Extracapsular Extension in Papillary Thyroid Cancer

“…Shimamoto et al 14 studied sonographic prediction in staging of papillary cancer and found that the sensitivity of sonography for detection of extracapsular extension of a tumor into the prethyroidal muscles and sternocleidomastoid was 77.8%, but the sensitivity values for invasion into the trachea and the esophagus were only 49% and 28.6%, respectively. That study, from 1998, used lower-frequency transducers (7.5-10 MHz) than our study (12)(13)(14)(15)(16)(17)(18) and was performed before the widespread use of harmonic imaging, compound imaging, and other sonographic techniques that have improved the resolution of sonography in current practice. A different study by Yamamura et al 15 from 2002 had much better results using preoperative sonography for detection of cancer invasion of the airways and found that sonography had an 83.3% accuracy rate, which was better than magnetic resonance imaging or computed tomography.…”

“…Fourth, we excluded microcarcinomas in our study, for which treatment remains controversial. Some authors suggest that microcarcinomas may be safely observed, 13,17 and a recent article by Chéreau et al 18 suggested that microcarcinomas with extracapsular extension have outcomes that are similar to those of T2 disease. Although we think this topic requires further investigation, because of the retrospective nature of our study we excluded microcarcinomas to accurately correlate pathologic results with sonographic findings.…”

“…As part of our diagnostic sonographic examination protocol, patients were placed in the supine position with the neck slightly hyper extended. A high-frequency linear transducer (12)(13)(14)(15)(16)(17)(18) with harmonic imaging was used to image the neck in both transverse and longitudinal views using grayscale imaging with color or power Doppler imaging, or both.…”

Contrastive study of two screening criteria for active surveillance in patients with low-risk papillary thyroid microcarcinoma: a retrospective analysis of 1001 patients

“…However, 5 mm as measured by examination certainly could be an appropriate threshold for treatment with surveillance. In addition, Moon et al [ 24 ] found that only 1.2% of thyroid malignant nodules measuring ≤5 mm on ultrasonography increased to >3 mm within 12 months, indicating that PTMC lesions of ≤5 mm were less likely to develop. Their study also supports our findings.…”

Hypothyroidism-Associated Autoimmune Thyroiditis and Papillary Thyroid Cancer

“…Many studies agree that there is no significant enlargement during follow-up in most of cases [7]. In small nodes (for instance smaller than 5 mm) the cytological report may bring some benefits in cases with changes of the diameters over time [8].…”