Post-thyroidectomy neck ultrasonography in patients with thyroid cancer and a review of the literature

Abstract

The importance of routine neck ultrasonography for the detection of unsuspected local or nodal recurrence of thyroid cancer following thyroidectomy (with or without neck dissection) is well documented in many journal articles and international guidelines. Herein, we present a pictorial summary of the sonographic features of benign and malignant central neck compartment nodules and cervical lymph nodes via a series of high-quality ultrasonographic images, with a review of the literature.

Fig. 1

Normal appearance of the central neck compartment post thyroidectomy. US images show (a) uniform echogenic texture owing to fibrofatty connective tissue in the thyroid bed (arrowhead); and (b) the left thyroid bed occupied by the oesophagus (arrow).

Fig. 2

Benign thyroid bed nodule. US images show (a) a benign thyroid bed nodule (arrowheads) in a patient whose histopathology was unavailable, but the nodule was assumed to be benign, as the patient’s thyroglobulin level had been 0.2 UG/L for at least 6 years; and (b) a nodule that contains linear internal echoes that are parallel to the surrounding tissue plane on longitudinal section.

Fig. 3

US images show central neck compartment findings suspicious for malignancy. Subsequent biopsy confirmed recurrence. US images show (a) round, hypoechoic nodules (arrow), typical of recurrences, situated between the carotid artery and trachea; and (b & c) the hyperechoic appearance of metastases from papillary carcinoma of thyroid (arrowheads) due to the deposition of thyroglobulin. Recurrence shown in (c) was subsequently confirmed to be the insular type of thyroid carcinoma on histopathology.

Fig. 4

Histopathology-proven recurrent papillary thyroid carcinoma. US image shows central neck recurrences with heterogeneous internal echoes and cystic components (arrows). Cystic necrosis, as shown here, is more frequently seen in papillary carcinomas.

Fig. 5

Benign lymph nodes. (a) US image shows normal nodes and reactive hyperplastic nodes characterised by an elongated shape and a well-defined echogenic hilum, which is continuous with the adjacent fat (black arrowhead). (b) Power Doppler image shows vascularity entering the centre or hilum of the node and extending toward each tip.

Fig. 6

(a & b) US images show a 24 mm × 10 mm × 3 mm benign hyperplastic lymph node (arrows) with its vascular supply entering the fatty hilum.

Fig. 7

US image shows a small elongated node measuring less than 5 mm, which can be assumed to be benign. An echogenic fatty hilum may not be identifiable in small nodes, particularly those that are less than 5 mm. These small elongated nodes are commonly encountered in clinical practice and can be assumed to be benign.

Fig. 8

US image shows a small and somewhat rounded node (in contrast to the elongated shape of a benign node), which may indicate indeterminate or not completely benign-appearing nodes. Also, these nodes may not show the echogenic hilum. When such indeterminate findings are encountered, a definite course of action may not be apparent. Management decisions should incorporate the patient’s risk profile and serum thyroglobulin levels. A practical decision-making flow-chart is presented in Fig. 9.

Fig. 9

Flowchart of patient management of indeterminate/not completely benign nodes.(16) FNA: fine-needle aspiration; Tg: thyroglobulin; US: ultrasonography

Fig. 10

US images show (a) nodal calcification in metastatic nodes from papillary thyroid cancer, which is usually fine or punctate (arrowhead), representing calcified psammoma bodies; and (b) metastatic lymph node with ill-defined margin, containing peripheral calcifications (arrow). Nodes suspicious for malignancy may show the following features: presence of calcifications, cystic or necrotic change, rounded or irregular shape, inhomogeneous internal echopattern, abnormal vascularity, and loss of echogenic hilum.

Fig. 11

US image shows a lymph node with a combination of peripheral and hilar vascularity, which is highly suspicious for malignancy. Nodes showing peripheral vascularity that does not arise from the hilar vessels or a combination of peripheral and hilar vascularity, are highly suspicious for malignancy. These peripheral or capsular vessels are recruited in response to pro-angiogenesis factors released by tumour cells.⁽¹⁷⁾

Fig. 12

US images show (a) a malignant lymph node containing a cystic area (arrowhead); and (b) intranodal vascularity being displaced in the presence of cystic necrosis.

Fig. 13

Advanced nodal disease with local infiltration of adjacent structures is infrequently encountered. (a) Longitudinal US image shows an echogenic mass within the lumen of the right internal jugular vein in a patient with papillary thyroid cancer. (b) Correlative CT image confirms the infiltration of the right internal jugular vein by adjacent metastatic lymph node (arrow). Tumour recurrence in the right thyroid bed is apparent (asterisk).