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BOOKLET to Provide Basic Information Regarding Health Effects of Radiation (3rd edition)

Occult (Latent) Thyroid Cancer

Occult (Latent) Thyroid Cancer_Figure

Some types of cancer present no symptoms and exert no effects on people's health throughout their lifetime and are not clinically detected but are later found through histopathology diagnosis (including postmortem autopsy). Such cancer is called occult (latent) cancer.

Thyroid cancer is mostly a differentiated cancer in which cancer cells are mature and grow slowly. No symptoms appear over a lifetime in some cases. Such differentiated thyroid cancer is sometimes found as an occult (latent) cancer only through an autopsy conducted after a person's death due to other causes.

Based on an analysis using the cancer registry, probabilities that a Japanese person will develop thyroid cancer during his/her lifetime are 0.78% for female and 0.23% for male.*1 For example, there was a report that as a result of postmortem autopsies for 102 cases conducted in Sendai in 1975, occult differentiated thyroid cancer was found in 29 cases (prevalence rate: 28.43%).*2 These results also show that in many cases, thyroid cancer is an occult (latent) cancer without symptoms over a lifetime.


*1: Kamo K et al., “Lifetime and Age-Conditional Probabilities of Developing or Dying of Cancer in Japan” Jpn. J. Clin. Oncol. 38(8) 571-576, 2008.

*2: Fukunaga FH, Yatani R., “Geographic pathology of occult thyroid carcinomas ” Cancer 36:1095-1099, 1975.

  • Included in this reference material on March 31, 2020
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