Roles of ultrasonography and computed tomography in the surgical management of cervical lymph node metastases in papillary thyroid carcinoma
Introduction
Papillary thyroid carcinoma (PTC) characteristically spreads early to regional lymph nodes, but rarely causes distant metastases.1, 2 PTC involves metastasis to cervical lymph nodes in 30–80% of patients,2, 3 and recent studies have revealed that regional lymph node metastasis has an adverse prognostic impact on survival, especially in older patients (≥45 years).4, 5 PTC recur most frequently at the cervical lymph nodes; loco-regional recurrences are reported in up to 31% of patients.6, 7, 8 Such high rates of recurrence suggest that many patients have lymph node metastases at the time of initial surgery, and that if these metastases can be detected and removed, future cervical recurrence and patient morbidity will be reduced.9
The indications for, and extent of, lymph node dissection are the most contested issues in the surgical management of PTC. Therapeutic central or lateral compartment neck dissection should be performed for patients who have PTC with clinically apparent cervical lymph node metastasis detected by palpation or imaging studies.10, 11 Prophylactic central compartment neck dissection (CCND) may be performed in patients with PTC, especially for advanced T3 and T4 tumors, while prophylactic lateral compartment neck dissection (LCND) is not generally recommended, according to the American Thyroid Association (ATA) guidelines.12 Because neck dissection can result in postoperative complications such as hypocalcemia, recurrent laryngeal nerve palsy, hematoma, chyle leakage, and spinal accessory nerve dysfunction, the indications for neck dissection should be carefully investigated.12, 13
Therefore, in order to make treatment decisions regarding neck dissection, it is very important that clinicians evaluate cervical lymph node metastasis adequately. Lymph node metastasis may be preoperatively evaluated by palpation or imaging tests including ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET). Although US is the most routinely recommended of these imaging methods for primary preoperative evaluation of lymph node metastases in patients with PTC,12 CT is also very useful in practice. There have been several studies exploring the features and diagnostic value of US and CT,14, 15, 16 but there are only a few studies which compare the utility of physical examination, US, and CT in determining the surgical plan for neck dissection from the surgeon's point of view. Therefore, the aim of this study was to compare the accuracy of physical examination, US, and CT in the preoperative detection of cervical lymph node metastasis and to evaluate how these methods influence the surgical management of the neck in patients with PTC.
Section snippets
Patients
We retrospectively reviewed medical records and imaging findings for 252 patients with PTC who underwent thyroidectomy and CCND with/without LCND from January 2007 to May 2010. This study was approved by the Institutional Review Board of Hanyang University Hospital. The diagnosis of PTC was confirmed pathologically for all patients after thyroidectomy. The characteristics of patients and tumors are summarized in Table 1. The patient group included 207 females and 45 males, and the median age
Thyroidectomy and neck dissection
Of the patients analyzed, 226 underwent total thyroidectomy, and 26 unilateral lobectomy. Prophylactic or therapeutic CCND was performed on all patients, based on preoperative imaging findings. Of the total of 252 patients (410 lymph node levels), 112 had metastatic lymph nodes in the central compartment (133 lymph node levels). Therapeutic LCND was performed for 41 patients (148 lymph node levels). Of these 41 patients, 32 had metastatic lymph nodes in the lateral compartment (74 lymph node
Palpation of cervical lymph nodes
In the past, the identification of cervical lymph node metastases was based primarily on palpation.21 The introduction of diagnostic imaging modalities such as US, CT, MRI, and PET has increased detection of non-palpable cervical lymph node metastases. In this study, only 7% of the patients had palpable nodes in the lateral neck, and no patients had palpable nodes in the central neck. Because of their anatomic locations, enlarged cervical lymph nodes may not be easily palpable, especially when
Conclusions
The roles of preoperative US and CT in surgical planning for central compartment neck dissection in PTC are limited by low sensitivity in the central neck, but US and CT may be useful in cases with non-palpable lateral neck nodes. Therefore, more sensitive and accurate methods are required to improve the detection of small lymph node metastasis in the central neck.
Conflict of interest statement
None of the authors have any conflict of interest or financial ties to disclose.
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