Papillary thyroid carcinoma: different clinical behavior among pT3 tumors

pT3 papillary thyroid carcinoma (PTC) can be divided into three subgroups according to the largest diameter >4 cm or evidence of minimal extrathyroidal extension (ETE): A >4 cm, no ETE; B ≤4 cm, with ETE; and C >4 cm, with ETE. The aim of this study was to analyze whether these subgroups are clinically different. A retrospective analysis of clinicopathological data of patients with pT3 PTC, with a minimum follow-up of 2 years, at a referral center was conducted. Outcome was evaluated after primary treatment and after 2 and 5 years of follow-up. Patients were classified as no evidence of disease (NED), biochemical evidence of disease (BED), and structural evidence of disease (SED) either locoregional (SED-L) or at distance (SED-D). The study patients were classified into three groups as follows: Group A (n = 91), Group B (n = 101), and Group C (n = 23). Most patients were female (80.0 %); mean age at diagnosis was 49.9 ± 16.5 years. 214 patients underwent total thyroidectomy; 208 patients were treated with (131)I. Median follow-up was 6.0 years. After primary treatment, the condition of NED was significantly different between the groups (A-87.9 %, B-68.3 %, C-43.5 %; p < 0.001). Recurrence rate, either biochemical or structural, was 8.8, 7.2, and 30.0 % in groups A, B, and C, respectively. Clinical status after 2 years anticipated clinical status after 5 years, except for Group B. ETE and tumor size were found to be predictors of disease status after primary treatment and after 2 years. ETE appeared as the strongest predictor of persistence of disease after primary treatment as well as of evidence of disease, either biochemical or structural, after 2 years of follow-up.