Abstract
IMPORTANCE: Tall cell morphology (TCM) is a rare and aggressive variant of papillary thyroid carcinoma (PTC) that has been associated with poor outcomes; however, the risk factors for worse survival are not well characterized. OBJECTIVE: To identify prognostic factors associated with cancer recurrence and death in patients with PTC-TCM. DESIGN, SETTING, AND PARTICIPANTS: All patients treated for PTC-TCM at a single tertiary-level academic health care institution from January 1, 1997, through July 31, 2018, were included. Tall cell variant (TCV) was defined as PTC with TCM of 30% or more; and tall cell features (TCF) was defined as PTC with TCM of less than 30%. Patients with other coexisting histologic findings and/or nonsurgical management were excluded. Clinicopathologic features associated with worse outcomes were identified using Kaplan-Meier and Cox proportional-hazards model. Data were analyzed from March 1, 2018, to August 15, 2018. MAIN OUTCOMES AND MEASURES: Locoregional recurrence-free survival (LRRFS), distant recurrence-free survival (DRFS), and overall survival (OS) after surgery. RESULTS: A total of 365 patients (median [range] age, 51.8 [15.9-91.6] years; 242 [66.3%] female) with PTC-TCM (TCV, 32%; TCF, 68%) were evaluable. Total thyroidectomy was performed in 336 (92%) patients; 19 (5.2%) received radiotherapy; and 15 (4.1%) received radioactive iodine. Clinical features were pT3 or T4, 65%; node-positive, 53%; and positive surgical margins, 24%. LRRFS at 1-, 3-, 5-, and 10-year was 95%, 87%, 82%, and 73%, respectively. On multivariable analysis, male sex and age were not independent predictors of inferior 5-year LRRFS, whereas positive surgical margins (HR, 3.5; 95% CI, 2.0-6.3), positive lymph nodes (HR, 2.8; 95% CI, 1.4-5.8), and primary tumor size of 3 cm or more (HR, 3.3; 95% CI, 1.4-7.8) were strongly associated with worse LRRFS. Age 55 years or older (HR, 3.2; 95% CI, 1.5-7.0), male sex (HR 4.5; 95% CI, 2.1-10.0), positive surgical margins (HR, 2.7; 95% CI, 1.2-6.0), nodal positivity (HR, 3.1; 95% CI, 1.3-7.7), tumor diameter of 1.5 cm or more (HR, 20.6; 95% CI, 2.8-152.1), and TCV vs TCF (HR, 3.1; 95% CI, 1.5-6.7) were associated with worse DRFS. Male sex (HR, 3.1; 95% 1.4-6.8) and tumor diameter of 1.5 cm or more (HR, 2.8; 95% CI, 1.0-7.4) were associated with worse OS. A findings-based nomogram was constructed to predict 10-year LRRFS (C index, 0.8). CONCLUSIONS AND RELEVANCE: This retrospective cohort study found that in patients with PTC-TCM, positive surgical margins, node positive disease, and tumor size of 3 cm or more were risk factors for worse LRRFS. Intensified locoregional therapy, including adjuvant radiation, may be considered for treating these patients.