Lateral cervical lymph node metastasis (LLNM) is a well-established prognostic factor influencing recurrence and survival in patients with papillary thyroid carcinoma (PTC). However, the accuracy of preoperative imaging examinations is limited. We have pioneered a minimally invasive technique-endoscopic thyroidectomy via sternocleidomastoid muscle posteroinferior approach (ETSPIA). This technique facilitates selective lateral neck lymph node dissection while excising thyroid lesions, effectively eradicating occult lateral cervical lymph node metastasis (OLLNM) without the need for extended incisions. This study investigates the diagnostic and therapeutic value of ETSPIA in managing OLLNM in PTC.A retrospective analysis was conducted on the clinical data of 142 patients with primary PTC who underwent ETSPIA at Beijing Tongren Hospital from November 2022 to June 2024. All patients underwent lateral cervical lymph node exploration: intraoperative examination first targeted the medial lymph nodes of the internal jugular vein, with frozen section analysis; if positive, the external lymph nodes of the internal jugular vein were subsequently addressed. The study recorded cases of LLNM and analyzed factors influencing OLLNM.Excluding 8 patients with preoperatively detected evident LLNM via ultrasound, 33 out of 134 patients (24.6%) exhibited OLLNM. This subgroup included 19 males and 14 females, with a median age of 34 years. The tumor-node-metastasis (TNM) staging revealed 17 cases of T1a, 7 cases of T1b, 4 cases of T2, and 4 cases of T3b. The tumors were located in the thyroid upper pole in 12 cases, the middle part in 15 cases, and the lower pole in 6 cases, with 26 cases presenting with solitary tumors and 7 with multiple lesions. Extrathyroidal extension was observed in 4 cases. Over a median follow-up period of 17 months, no severe complications were reported. Univariate analysis identified male gender, younger age, tumor T stage, preoperative ultrasound indication of upper pole thyroid tumors, and extrathyroidal extension as factors associated with OLLNM (P<0.001, P=0.02, P=0.007, P<0.001, P=0.003 respectively). Multivariate regression analysis demonstrated that male gender, younger age, and preoperative ultrasound indication of upper pole thyroid tumors were independent risk factors for OLLNM in PTC (P=0.001, P=0.006, P=0.02, P=0.002, respectively).As a novel minimally invasive endoscopic thyroid approach, ETSPIA allows for the excision of thyroid lesions while addressing lateral cervical metastatic lymph nodes. It demonstrates favorable cosmetic outcomes and safety, offering a viable alternative for the management of thyroid cancer.2024 AME Publishing Company. All rights reserved.