TABLE 1.
Characteristics of the studies included in this review.
| First author | Publication year | Study period (year/month) | Location | Sample size (n) | Research type | |
| Prevalence | Belfior et al. (44) | 1992 | 1980–1990 | Italy | 5637 | Retrospective study |
| Teng et al. (45) | 2006 | 1999–2004 | China | 3018 | Prospective study | |
| Wang et al. (46) | 2021 | 2017/01-2019/12 | China | 51637 | Retrospective study | |
| Mitro et al. (47) | 2016 | 2001–2009 | Thailand | 2749 | Prospective study | |
| Zhang et al. (49) | 2019 | 2014–2018 | China | 2495 | Prospective study | |
| Clero et al. (51) | 2012 | 1979–2004 | France | 600 | Retrospective study | |
| Kim et al. (54) | 2016 | 2010/11-2013/05 | Korea | 1170 | Retrospective study | |
| Zeng et al. (55) | 2020 | 1986–2018 | China | 34213 | Retrospective study | |
| Dong et al. (60) | 2013 | 1992/01-2009/12 | China | 1239 | Prospective study | |
| Zhao et al. (61) | 2017 | 2013/11-2015/03 | China | 2041 | Retrospective study | |
| Horn-Ross et al. (62) | 2001 | 1992–1998 | America | 1166 | Retrospective study | |
| Zhou et al. (65) | 2017 | 2013/02-2013/09 | China | 261 | Retrospective study | |
| Hou et al. (66) | 2020 | 2017/01-2019/03 | China | 506 | Retrospective study | |
| Kim et al. (69) | 2021 | 2010/04-2014/12 | Korea | 946 | Retrospective study | |
| Lymphatic metastasis | Wang et al. (70) | 2014 | 2010/06-2011/06 | China | 460 | Retrospective study |
| Zeng et al. (71) | 2021 | 2015/05-2020/11 | China | 359 | Retrospective study | |
| Zhao et al. (72) | 2019 | 2013/11-2018/02 | China | 4040 | Retrospective study | |
| BRAF mutation | Vuong et al. (77) | 2016 | 2006–2014 | Japan | 194 | Retrospective study |
| Kowalska et al. (78) | 2016 | 2000–2013 | Poland | 723 | Retrospective study | |
| Guan et al. (79) | 2009 | – | China | 1032 | Cross-sectional study | |
| Kim et al. (80) | 2017 | 2010/11-2015/03 | Korea | 215 | Retrospective study | |
| Lee et al. (81) | 2017 | 2015/03-2015/12 | Korea | 300 | Retrospective study |