{'fraction_non_alphanumeric': 0.04812575574365175, 'fraction_numerical': 0.0403869407496977, 'mean_word_length': 5.011627906976744, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 1, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
8th edition of the AJCC/TNM staging system of thyroid cancer: what to expect (ITCO#2).

Differentiated thyroid cancer (DTC) has become one of the most frequently diagnosed malignancies, especially among women and young adults (Davies & Welch 2014). The outcomes are generally very good: disease recurrence rates are low (Durante et al. 2013), and survival rates are excellent (Tuttle et al. 2017a). Evidence-based management is crucial to avoid overtreatment of these low-risk tumors, which can reduce quality of life and yet identify accurately those requiring more aggressive therapy. Several staging systems have been generated to inform DTC management. One of the most widely used is the tumor-node-metastasis (TNM) classification elaborated by the American Joint Committee on Cancer (AJCC), which allows to predict the risk of cancer-related death. The 8th edition of the AJCC staging system for thyroid cancer (AJCC-8) was recently published (Tuttle et al. 2017b) and is scheduled to be implemented on 1 January 2018. Revision of the system was undertaken to address several specific limitations identified in the 7th edition (AJCC-7), which has been in use since 2009 (Tuttle et al. 2017a,b). The main changes (described in detail below and summarized in Table 1) are as follows: (1) an increase in the age threshold for defining high risk of thyroid cancer-related death and (2) a decrease in the unfavorable prognostic significance attributed to certain findings (i.e., cervical lymph node metastases and microscopic extrathyroidal extension (ETE), which has been re-defined to include only invasion of the perithyroidal muscle). To assess the impact of transitioning to the new AJCC-8 in terms of stage distribution and prevalence of each stage class, we analyzed data extracted from the web-based database of the Italian Thyroid Cancer Observatory (ITCO) (www.itcofoundation.org), a network of thyroid cancer centers (including primary and tertiary centers) located throughout Italy. The database includes prospectively updated, observational data provided by ITCO member centers on patients consecutively diagnosed with thyroid cancer since 2013 (Lamartina et al. 2017). Cases included in our study met all the following criteria: (1) histological diagnosis of thyroid cancer of follicular origin; (2) date of diagnosis between 1 January 2013 and 1 March 2017; (3) complete data on primary tumor pathology, including minimal ETE, and initial treatment. The selected cohort analyzed included 1765 patients, 76% of whom were females. The median age at diagnosis was 48 years (range: 10–87). Total thyroidectomy (or lobectomy + completion thyroidectomy) was performed in 1727 (98%) cases and followed by radioiodine remnant ablation in 954 (55%). Neck dissection was performed in 711 (40%) of the 1765 patients. Most of the tumors (n = 1657, 94%) were papillary thyroid cancers; the remaining 108 (6%) were follicular or Hürthle cell carcinomas. Estimated risks of recurrence calculated according to the criteria recommended in 2015 by the American Thyroid Association were low in 1046 (59%), intermediate in 612 (35%) and high in 107 (6%) of the cases. Microscopic ETE was found in 410 (23%), but only 40 (2%) of these patients had gross invasion of the strap muscles (sternohyoid, sternothyroid, thyroidhyoid and/or omohyoid muscles). Lymph node status for the 711 patients who underwent lymph node dissection was as follows: pN0 (no metastasis) in 338 (19%); pN1a (central compartment metastases) in 221 (12%) and pN1b (lateral compartment metastases) 152 (9%). Distant metastases were found in 32 (1.8%) patients. As noted above, in the AJCC-8, the age threshold for high risk of disease-specific mortality was raised from 45 years – the median age at diagnosis in several published series – to 55 years (Nixon et al. 2016). This change increases the proportion of relatively young patients whose mortality risk can be defined solely on the basis of the absence or presence of distant metastases (stages I and II, respectively) (Table 1). As shown in Fig. 1A, the percentage of patients classified as ‘younger’ in our 3 25