Primary Tumor Location and Lymphatic Spread in Papillary Thyroid Carcinoma

OBJECTIVE: Papillary thyroid carcinoma (PTC) frequently metastasizes to cervical lymph nodes. Surgical planning is often based on the presumed central-to-lateral pattern of spread. The extent of central and lateral neck dissection remains controversial, with recommendations largely derived from small series. The study aimed to determine whether primary tumor location can guide the extent of neck dissection. STUDY DESIGN: Single-center retrospective cohort study. SETTING: Quaternary care center. METHODS: Patients with PTC undergoing primary thyroid surgery with a central and/or lateral neck dissection (CND and/or LND) between 1999 and 2023 were evaluated. Tumor location (superior, mid, inferior pole, or isthmus) was determined by ultrasound and confirmed on pathology. The primary outcome was pattern of nodal metastases by tumor location. RESULTS: Among 1688 patients (median age 45 years; 67% female), 99% underwent CND and 45% LND. Central neck positivity was similar across superior (79%; 262/333), inferior (73%; 286/393), mid (74%; 626/849), and isthmic (76%; 71/94) tumors (P = .22). On multivariable logistic regression, central neck positivity did not differ significantly (superior OR: 1.28 [95% CI, 0.74-2.23]; lower OR, 0.88 [95% CI, 0.52-1.50]; mid OR, 0.79 [95% CI, 0.48-1.32]; compared with isthmic. LND unadjusted and adjusted positivity rates were also comparable across primary tumor location. In patients undergoing LND, level III was most frequently involved (81%), followed by levels IV (75%), IIa (60%), Vb (36%), and IIb (9%) (P < .01). Lastly, superior pole tumors were significantly associated with ipsilateral level III involvement, compared with inferior and mid pole tumors (P < .01). CONCLUSIONS: In patients undergoing therapeutic neck dissection for PTC, primary tumor location did not predict nodal distribution and should not determine the extent of neck dissection.