Capsular extension at ultrasound is associated with lateral lymph node metastasis in patients with papillary thyroid carcinoma: a retrospective study.

BACKGROUND In patients with papillary thyroid cancer (PTC), cervical lymph node metastasis (LNM) must be carefully assessed to determine the extent of lymph node dissection required and patient prognosis. Few studies attempted to determine whether the ultrasound (US) appearance of the primary thyroid tumor could be used to predict cervical lymph node involvement. This study aimed to identify the US features of the tumor that could predict cervical LNM in patients with PTC. METHODS This was a retrospective study of patients with pathologically confirmed PTC. We evaluated the following US characteristics: lobe, isthmus, and tumor size; tumor position; parenchymal echogenicity; the number of lesions (i.e., tumor multifocality); parenchymal and lesional vascularity; tumor margins and shape; calcifications; capsular extension; tumor consistency; and the lymph nodes along the carotid vessels. The patients were grouped as no LNM (NLNM), central LNM (CLNM) alone, and lateral LNM (LLNM) with/without CLNM, according to the postoperative pathological examination. RESULTS Totally, 247 patients, there were 67 men and 180 women. Tumor size of > 10 mm was significantly more common in the CLNM (70.2%) and LLNM groups (89.6%) than in the NLNM group (45.4%). At US, capsular extension > 50% was most common in the LLNM group (35.4%). The multivariable analysis revealed that age (OR = 0.203, 95%CI: 0.095-0.431, P < 0.001) and tumor size (OR = 2.657, 95%CI: 1.144-6.168, P = 0.023) were independently associated with CLNM compared with NLNM. In addition, age (OR = 0.277, 95%CI: 0.127-0.603, P = 0.001), tumor size (OR = 6.069, 95%CI: 2.075-17.75, P = 0.001), and capsular extension (OR = 2.09, 95%CI: 1.326-3.294, P = 0.001) were independently associated with LLNM compared with NLNM. CONCLUSION Percentage of capsular extension at ultrasound is associated with LLNM. US-guided puncture cytology and eluent thyroglobulin examination could be performed as appropriate to minimize the missed diagnosis of LNM.