Repositorio Institucional (Univ. de la Frontera)

Carocca, Angel

On group actions on Riemann-Roch spaces of curves

Comparin, P

Non-symplectic automorphisms of order multiple of seven on K3 surfaces

Hirsch, Michael

Med Ultrason 2023, Vol. 25, no. 1, 93-97DOI: Pictorial essayPreoperative ultrasound study of differentiated thyroid cancer: relevant aspects for its optimal performance. Pictorial essay.Michael Hirsch1,2, Javiera Matus1,3, Constanza Orellana1,3, Karin Krauss41Programa de Radiología, Departamento de Especialidades Médicas, Universidad de La Frontera, 2Departamento de Imágenes, Clínica Alemana de Temuco, 3Servicio de Radiología, Hospital Hernán Henríquez Aravena, 4Servicio de Imagenología, Complejo Asistencial Padre Las Casas, Temuco, Chile.Received 25.08.2022 Accepted 17.12.2022 Med Ultrason 2023, Vol. 25, No 1, 93-97 Corresponding author: Michael Hirsch, MD  Departamento de Imágenes,   Clínica Alemana de Temuco  Senador Estébanez 645, 4810297 Temuco,  Región de La Araucanía, Chile  Phone: 56-45-2201167  E-mail: michael.hirsch@ufrontera.clIntroductionThe incidence of thyroid cancer has increased in last years, the differentiated thyroid carcinoma (DTC) being the most frequent type. Up to 95% of DTC are papillary thyroid carcinoma (PTC) [1]. Dissemination to regional lymph nodes is present in 30-80% of cases, mainly at cervical level VI (fig 1) [2,3], being the greatest risk fac-tor for thyroid cancer recurrence, suggesting that many of the lymphatic metastases detected in the first post-treat-ment years are residual disease [4]. Due to the greater risk of complications related to the surgical reinterven-tion, the interest for more accurate preoperative studies has increased, cervical ultrasound (US) being the most sensitive study, modifying the surgical approach in up to 23% of cases [4]. In this pictorial essay we present relevant aspects in the preoperative US evaluation of DTC and representa-tive images from our experience. Ultrasound techniqueA multi-frequency linear transducer (8-15 MHz) is preferable for the correct evaluation of the deep paratra-cheal areas and the tracheoesophageal grooves (TEG), which are references for the trajectory of the recurrent laryngeal nerves (fig 2) [5].The neck must be hyperextended. The patient should be asked to turn their neck to the right or left to facilitate the study of level VI lymph nodes and better expose the TEG (fig 3) [5].  The cervical region must be explored from the chin to the suprasternal region, looking for remnants of the thyroglossal duct, which are frequently close to the hyoid bone (fig 4), presence of pyramidal lobes and intrathorac-ic extension [5].Characterization of thyroid lesionsAlthough the aim of this work is not to review the features of thyroid nodules to allocate risk of malignan-cy, it must be remembered that the nodules at greatest AbstractDifferentiated thyroid cancer has an increasing incidence in recent years, but its mortality remains low. In this context, a preoperative ultrasound study is fundamental; it makes a difference due to its ability to adequately characterize local involve-ment, the presence of extrathyroidal extension and lymphatic metastases. A preoperative study can help to decide the best therapeutic measures and thus avoid adding greater morbidity to patients. In this article we present the relevant aspects to consider in the preoperative ultrasound evaluation of differentiated thyroid cancer and representative images of the main find-ings that can be found.Keywords: cancer; thyroid; ultrasound; metastasis; lymph nodes10.11152/mu-385894 Michael Hirsch et al Preoperative US study of differentiated thyroid cancer & its optimal performancerisk of malignancy are solid, hypoechogenic, taller than it is wide, with irregular edges, microcalcifications, inter-mittent ring-shaped calcifications and with extrathyroidal extension (ETE) [6].Evaluation of extrathyroidal extensionThe interruption of the capsule, bulging of structures, involvement of the TEG, contact of the tumor with the capsule, and tracheal invasion suggest ETE [7,8]. Inter-ruption of the capsule appears as a loss of the hypere-chogenic interface of the capsule [8]. The protrusion of a nodule towards the TEG is associated with an invasion of the recurrent laryngeal nerve [8]. Contact between the tumor and the adjacent capsule higher than 25% of the nodule circumference have a positive predictive value of 70.7% and a specificity of 85.7% for microcarcinomas (fig 5, fig 6) [7]. The formation of an obtuse angle be-tween the tumor and the trachea is suggestive of tracheal invasion (fig 7) [8]. It is also useful to evaluate the vocal cords and their adequate excursion; asymmetric displacement or absence of displacement of the affected side [9].Fig 1. Neck lymph node levels. Level I: submental (IA) and submandibular (IB). Level II: upper internal jugular chain. Level III: middle internal jugular chain. Level IV: lower inter-nal jugular chain. Level V: posterior triangle. Level VI: central (anterior) compartment. Level VII: superior mediastinal nodes. Sublevel IA and IB are separated by anterior bellies of both digastric muscles, level I and II by the vertical plane defined by the posterior border of the submandibular gland, sublevel IIA and IIB by the posterior border of the internal jugular vein, level II and III by the horizontal plane defined by the inferior border of the hyoid bone, level III and IV by the horizontal plane defined by the inferior border of the cricoid cartilage as well as sublevel VA and VB, level VI and levels III-IV by the medial borders of both common carotid arteries, and level VI and VII by superior border of manubrium.Fig 2. Left tracheoesophageal groove (dotted lines) between the trachea (asterisk) and the esophagus (arrow), through which the recurrent laryngeal nerve passes together with echogenic fatty tissue (arrowhead).Fig 3. US that shows how to improve the visualization of the right tracheoesophageal groove (TEG) (a). Turning the head to the left (b), the esophagus slides to the right, better exposing the TEG (dotted line) and its contents (arrowhead). Asterisk: trachea.95Med Ultrason 2023; 25(1): 93-97Assessment of the lymph nodes The presence of microcalcifications and cystic chang-es have a proven specificity of up to 100%, but low sen-sitivity for lymph node metastasis [10]. The presence of peripheral vascularization is the criterion of malignancy with a better sensitivity-specificity ratio (fig 8) [5].The loss of hyperechogenic hilum has shown a speci-ficity of only 29%. However, due to the high sensitivity Fig 7. Different cases of papillary thyroid carcinoma (PTC): a) PTC that presents an acute angle in relation to the trachea (asterisk), unlike b), which presents an obtuse angle, with this one being of greatest risk for tracheal invasion. Fig 4. US in the sagittal plane, midline, demonstrating a thy-roglossal duct cyst (between calipers) with anechogenic con-tent and a fine septum, immediately caudal to the hyoid bone (arrow). Asterisk: mylohyoid muscle, arrow heads: epiglottis.Fig 5. Different cases of papillary thyroid carcinoma (PTC) that present progressive involvement of the capsule up to the marked extrathyroidal extension: a) PTC completely surrounded by healthy parenchyma (arrow heads); b) PTC that comes in contact without involving the capsule (arrow heads), which presents a linear hyperechogenic appearance: c) PTC that involves the capsule (white ar-row heads), becoming hypoechogenic unlike the linear hyperechogenic appearance of the normal capsule (black arrow heads). There is no extension towards the infrahyoid muscles; d) PTC with marked extension towards the infrahyoid muscles (arrows), and towards the trachea with loss of definition of its cartilages and membrane (arrow heads). Asterisk: trachea.Fig 6. Papillary thyroid carcinoma (between calipers) that pre-sents protrusion towards the esophageal groove (arrowhead) without involving it completely. Asterisk: trachea, arrow: es-ophagus.96 Michael Hirsch et al Preoperative US study of differentiated thyroid cancer & its optimal performanceof this finding (100%), the presence of the fatty hilum makes it possible to exclude the presence of a malignan-cy with some certainty [10].Hyperechogenicity of the parenchyma and rounded morphology has shown specificity of only 18% and 54%, respectively, to determine malignancy; therefore, it is recommended that these criteria to be used with other auxiliary criteria such as increased size or those previ-ously mentioned [10,11].Limitations of USPreoperative computed tomography (CT) or magnet-ic resonance imaging (MRI) are recommended as a com-plement to US for patients with a clinical suspicion of advanced disease [12] (fig 9, fig 10). Patients who pres-ent voluminous or widely distributed adenopathies could present involvement of some lymphatic groups difficult to visualize with routine preoperative US [12].Staging of DTC  In the 8th edition of the American Joint Committee on Cancer (AJCC) from 2018, significant changes for the staging of patients with DTC were reported (23-35% of down-staging) [13]. These changes are meant to avoid the overtreatment of patients at low risk of malignancy [14,15].Active surveillanceActive surveillance is considered a safe option for managing patients with low-grade asymptomatic DTC <1 cm and with no high-risk factors such as the presence of metastatic lymph nodes, distant metastasis, a fine-nee-dle biopsy with findings of high-grade malignancy or Fig 8. Different cases of lymphatic metastasis of papillary thyroid carcinoma: a) adenopathy (arrowheads), with solid component of heterogeneous echogenicity and peripheral vascularization in color Doppler mode and anechogenic cystic component (arrow); b) adenopathy with loss of echogenic hilum, heterogeneous echostructure and microcalcifications; c) adenopathy with heterogeneous echostructure, loss of echogenic hilum and penetrating peripheral vessels in color Doppler mode; d) adenopathy of heterogeneous echostructure, loss of echogenic hilum, with presence of calcifications (arrow heads) and small peripheral cystic areas (arrows); e) adenopathy (arrow heads) of heterogeneous echostructure, with loss of echogenic hilum, isolated microcalcifications, emphasizing greater overall echogenicity than the adjacent sternocleidomastoid muscle (asterisk); f) adenopathy (arrow heads) with small cystic area, similar in appearance to a thyroid colloid cyst (arrow).Fig 9. Papillary thyroid carcinoma (arrowheads) that at the time of the study with ultrasound (a) presented an extension towards the mediastinum (arrows), which limited the complete assessment; b) CT of the same patient demonstrates the great intrathoracic involvement not visualized by ultrasound. White asterisk: trachea, black asterisk: sternum.97Med Ultrason 2023; 25(1): 93-97tumors that invade the trachea or the recurrent laryngeal nerve [16]. ConclusionsNowadays, US is the best tool to conduct an adequate preoperative study of DTC. Whoever does the preopera-tive study must be familiar with the relevant aspects of the technique, important findings that must be assessed and added to the report, as well as an in-depth understanding of anatomy and ultrasound signs that can differentiate conditions that will mark the prognosis and therapeutic approach. Emphasis must be placed on the evaluation of ETE and lymphatic involvement and complemented with additional studies in cases where US is insufficient.Conflict of interest: noneReferences1. Tian X, Song Q, Xie F, et al. Papillary thyroid carcinoma: an ultrasound-based nomogram improves the prediction of lymph node metastases in the central compartment. Eur Ra-diol 2020;30:5881–5893.2. Kocharyan D, Schwenter F, Bélair M, Nassif E. The rel-evance of preoperative ultrasound cervical mapping in pa-tients with thyroid cancer. Can J Surg 2016;59:113–117.3. O’Connell K, Yen TW, Quiroz F, Evans DB, Wang TS. The utility of routine preoperative cervical ultrasonography in patients undergoing thyroidectomy for differentiated thy-roid cancer. Surgery 2013;154:697–703.4. Kumbhar SS, O’Malley RB, Robinson TJ, et al. Why thy-roid surgeons are frustrated with radiologists: Lessons learned from pre- and postoperative US. Radiographics 2016;36:2141–2153.5. Yeh MW, Bauer AJ, Bernet VA, et al. American thyroid association statement on preoperative imaging for thyroid cancer surgery. Thyroid 2015;25:3–14.6. Moon WJ, Baek JH, Jung SL, et al. Ultrasonography and the ultrasound-based management of thyroid nodules: Con-sensus statement and recommendations. Korean J Radiol 2011;12:1–14.7. Kwak JY, Kim EK, Youk JH, et al. Extrathyroid extension of well-differentiated papillary thyroid microcarcinoma on US. Thyroid 2008;18:609–614.8. Chung SR, Baek JH, Choi YJ, et al. Sonographic assess-ment of the extent of extrathyroidal extension in thyroid cancer. Korean J Radiol 2020;21:1187–1195.9. Leboulleux S, Girard E, Rose M, et al. Ultrasound crite-ria of malignancy for cervical lymph nodes in patients followed up for differentiated thyroid cancer. J Clin Endo-crinol Metab 2007;92:3590–3594.10. Yeh MW, Bauer AJ, Bernet VA, et al. American thyroid association statement on preoperative imaging for thyroid cancer surgery. Thyroid 2015;25:3–14.11. Zhao H, Li H. Meta-analysis of ultrasound for cervical lymph nodes in papillary thyroid cancer: Diagnosis of cen-tral and lateral compartment nodal metastases. Eur J Radiol 2019;112:14–21.12. Haugen BR, Alexander EK, Bible KC, et al. 2015 Ameri-can Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: The American Thyroid Association Guidelines Task Force on Thyroid Nodules and Differentiated Thyroid Cancer. Thyroid 2016;26:1–133.13. Brierley J, Gospodarowicz M, Wittekind C. TNM Classi-fication of Malignant Tumours, 8th Edition. Wiley-Black-well, 2017.14. Kim M, Kim WG, Oh HS, et al. Comparison of the Sev-enth and Eighth Editions of the American Joint Committee on Cancer/Union for International Cancer Control Tumor-Node-Metastasis Staging System for Differentiated Thy-roid Cancer. Thyroid 2017;27:1149–1155.15. Tuttle RM, Haugen B, Perrier ND. Updated American joint committee on cancer/tumor-node-metastasis staging system for differentiated and anaplastic thyroid cancer (Eighth Edi-tion): What changed and why? Thyroid 2017;27:751–756.16. Sakai T, Sugitani I, Ebina A, et al. Active surveillance for T1bN0M0 papillary thyroid carcinoma. Thyroid 2019;29:59–63.Fig 10. Papillary thyroid carcinoma (arrowheads) that at the time of the study with ultrasound (a) presented an extension towards the trachea (asterisk), difficult to characterize; b) CT of the same patient better demonstrates the tracheal invasion (arrow heads). Asterisk: trachea.

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