Takano Toru
Department of Metabolic Medicine, Osaka University Graduate School of Medicine, Suita 565-0871, Japan.
Endocr J. 2017 Mar 31;64(3):237-244. doi: 10.1507/endocrj.EJ17-0026. Epub 2017 Feb 2.
Thyroid cancers have long been considered to arise in middle age and, after their repeated proliferation, resulting in further damage to the genome, they progress to more aggressive and lethal cancers. However, in 2014, some studies were reported that might lead to a marked change in our understanding of the natural history of thyroid cancer. A high prevalence of papillary carcinoma in the young suggested that the first initiation of thyroid cancer is likely to occur in the infantile period. Such a conclusion was also supported by a very slow growth rate of papillary microcarcinomas (PMCs) in an observation trial. The proliferation rate of PMCs was negatively correlated with the age, and surgery to remove PMCs did not contribute to reduce mortality from thyroid cancer. These findings strongly suggested the existence of self-limiting cancers, which are truly malignant but do not progress to lethal cancers, for the first time in human history. The early detection of self-limiting cancers results in overdiagnosis. Ultrasonographic screening of the thyroid in the young should be avoided. Lethal thyroid cancers, whose origin is still unknown, appear suddenly after middle age. In the elderly, thyroid cancers are a mixture of self-limiting and lethal cancers; thus, when thyroid cancer is detected, careful follow-up with examination of its growth rate is required.
甲状腺癌长期以来被认为发生于中年，在反复增殖后，导致基因组进一步受损，进而发展为更具侵袭性和致命性的癌症。然而，2014年有一些研究报道，可能会使我们对甲状腺癌自然史的理解发生显著变化。年轻人中乳头状癌的高发病率表明，甲状腺癌很可能在婴儿期首次发生。一项观察性试验中乳头状微小癌（PMCs）非常缓慢的生长速度也支持了这一结论。PMCs的增殖率与年龄呈负相关，切除PMCs的手术对降低甲状腺癌死亡率并无帮助。这些发现首次有力地表明，在人类历史上存在自限性癌症，它们确实是恶性的，但不会发展为致命性癌症。自限性癌症的早期检测会导致过度诊断。应避免对年轻人进行甲状腺超声筛查。起源仍不明的致命性甲状腺癌在中年后突然出现。在老年人中，甲状腺癌是自限性和致命性癌症的混合体；因此，当检测到甲状腺癌时，需要仔细随访并检查其生长速度。
