Diffuse Sclerosing Variant of Papillary Thyroid Carcinoma Is Associated With Aggressive Histopathological Features and a Poor Outcome: Results of a Large Multicentric Study

{Context: Diffuse sclerosing variant (DSV) is a rare and aggressive subtype of papillary thyroid carcinoma (PTC). Objective: The objective of the study was to investigate the clinicopathological features and prognosis of DSV patients and compare these findings with all other PTCs and high-risk PTCs. Design and Setting: The data of patients who underwent surgery for DSV and PTC between 2003 and 2014 in seven surgical departments specialized in endocrine surgery were reviewed. Patients: Fifty-six DSV patients were included (mean age 32.6 +/- 12.5 y; 46 [82%] female) and were compared with 2945 non-DSV PTCs and 48 high-risk PTCs. Results: Forty-six DSV patients (82%) were pT3, 43 (77%) had an extrathyroidal extension, and 54 (96%) had lymph node metastasis, including 48 patients with involvement in the lateral compartment (86%). During the follow-up period of 4.3 +/- 2.3 years, 19 patients (34%) had a recurrence, including 18 patients with an ipsilateral lateral compartment recurrence. The only prognostic factor for recurrence in the multivariate analysis was extranodal extension (odds ratio 3.4 [1.1; 10.8]). The 7-year recurrence-free survival (RFS) was 63%. The RFS was significantly worse in patients with DSV than in other PTC patients (hazard risk 8.5 [5.2; 13.9], P < .0001) and were similar to the RFS of high-risk PTCs (hazard risk 1.1 [0.6; 2.2]