The cancer Korean women have most often lived with is not breast cancer but thyroid cancer. Of 1,538,962 women counted as cancer survivors, 470,948 — three in ten — had it.
1. How common is it. Of 1,538,962 Korean women counted as cancer survivors, 470,948 had thyroid cancer — three in ten, ahead of breast cancer.
2. How dangerous is it. Its five-year relative survival is 100.2%, the highest among major cancers (breast 94.7%, stomach 78.6%). Common and dangerous are different questions.
3. Should you be screened. Thyroid cancer is not among the six cancers in Korea's national screening programme — and that omission is deliberate. The National Cancer Center's own guideline states that “those without any symptoms do not need ultrasound screening.” If you can feel a lump in the neck or have other suspicious signs, see a doctor.
What follows works through those three from National Cancer Information Center figures.
How common is it?
In 2023, 35,440 people in Korea were diagnosed with thyroid cancer — 69.3 per 100,000 population, which works out to roughly one person in 1,443 in a single year. The number splits sharply by sex and by age.
| Group | 2023 cases | Rank within that sex |
|---|---|---|
| Women | 26,114 | 2nd among cancers in women |
| Men | 9,326 | 6th among cancers in men |
| Total | 35,440 | 1st of all cancers by incidence |
That is 2.8 times as many women as men. By age, it concentrates in the forties.
| Age band | Share of cases | Cases |
|---|---|---|
| 40s | 26.9% (highest) | about 9,533 |
| 50s | 22.9% | about 8,116 |
| 30s | 20.7% | about 7,336 |
| Three bands combined | 70.5% | about 24,985 |
Rankings by age band show the same shape. Thyroid cancer is the most common cancer both from 15 to 34 and from 35 to 64, and then drops out of the top five entirely past 65, where lung, colorectal, stomach, prostate and liver cancers lead. Not because it stops occurring, but because those rise so much faster with age.
In short, it is the cancer most often met by women in their thirties to fifties. Other health questions common to that group are covered in bone health, menopause and iron deficiency.
How dangerous is it?
Starting with the number: a five-year relative survival rate of 100.2%, the highest among major cancers.
| Cancer | 5-year relative survival | 2023 cases | People living with it |
|---|---|---|---|
| Thyroid | 100.2% | 35,440 | 587,292 |
| Breast | 94.7% | 29,871 | 354,699 |
| Stomach | 78.6% | 28,943 | 366,717 |
| Lung | 42.5% | 32,953 | 141,143 |
| All cancers | 73.7% | 288,613 | 2,732,906 |
One row pair stands out. Thyroid and lung cancer are diagnosed in almost the same numbers each year (35,440 against 32,953, a gap of 7.5%), yet the number of people living with them differs by 4.16 times. When the same number arrive and a different number accumulate, what differs is how long people remain.
But 100.2% does not mean everyone survives. The word doing the work is “relative.”
“Five-year relative survival — the probability that a cancer patient survives five years, compared with the general population.”
“A relative survival rate of 100% means survival equal to the general population; thyroid cancer exceeding 100% means that, on the figures alone, patients outlive the general population.”
— press coverage of a Ministry of Health and Welfare / Korea Central Cancer Registry release (January 2026). Not an agency text.
So 100.2% is closer to “about the same as a comparable person without it” than to a headcount. The article itself hedges with “on the figures alone.”
The other thing to hold alongside it is that thyroid cancer is not one disease. By tissue type:
| Type | 2023 cases | Share |
|---|---|---|
| Papillary | 33,498 | 94.5% |
| Follicular | 1,016 | 2.9% |
| Medullary | 148 | 0.4% |
| Anaplastic | 83 | 0.2% |
| Unspecified | 477 | 1.3% |
Nine in ten are papillary. But 83 anaplastic cases sit under the same name, and they behave nothing alike. Survival by tissue type is not in this source, so we have not carried the figures over into “mostly papillary, therefore mild.” A high overall survival rate and a mild individual case are different statements.
Should you be screened? It is not in the national programme
Despite ranking first among women, thyroid cancer is not in Korea's free national cancer screening programme. That covers six: stomach, colorectal, liver, breast, cervical and lung (details in the national screening article).
The omission is deliberate. The National Cancer Center issued a separate thyroid cancer screening recommendation, and its conclusion reads:
“Those without any symptoms do not need screening by ultrasound.”
“Anyone with symptoms suggestive of thyroid cancer, such as a palpable lump in the neck, should see a doctor for consultation.”
— press coverage of the National Cancer Center's 2015 thyroid cancer screening recommendation. The recommendation itself is posted under the Center's seven-cancer screening guidelines.
The background was a debate about overdiagnosis. Sweeping asymptomatic people with ultrasound finds small cancers that would never have caused trouble, and surgery and lifelong medication follow. The sharp fall in incidence from 2012 to 2015 shown below coincides with that debate.
Which makes the practical answer something like this.
| Your situation | What the recommendation says |
|---|---|
| No symptoms | There is no need to seek out an ultrasound |
| A palpable lump in the neck | Not screening — see a doctor |
| Voice changes or difficulty swallowing | The same — have it looked at |
| It is bundled into a health check you are having anyway | Fine, but agree in advance what happens if a small nodule turns up |
The symptom side — which signs to watch and how to read the test numbers — is covered separately in thyroid warning signs.
Is it still rising?
The 587,292 figure is 25 years of accumulation and says nothing about direction. Incidence trends do, and the shape is unusual.
“Thyroid cancer incidence rose 25.6% from 1999 to 2008 and 12.8% from 2008 to 2012, then fell −20.1% from 2012 to 2015. Since 2015, however, it has risen again, by an annual average of 3.9% through 2021.”
— National Cancer Information Center, analysis of cancer incidence trends
How large −20.1% is shows when set beside other cancers. The next largest decline is stomach cancer at −4.4% a year, and all cancers in women fell 6.2% over 2012–2015. The thyroid decline is three to four times either.
The climb back is also faster than average: from 2015 to 2021, all cancers in women rose 1.7% a year against thyroid cancer's 3.9%. One sharp break, then a gentle recovery. Neither “still climbing steeply” nor “now falling.”
The sex ratio has moved too. Women outnumbered men 3.26 to 1 in 2018 and 2.80 to 1 in 2023, because over those five years male cases rose 38.6% against 19.1% for women — twice the pace.
One subtraction worth doing
There is a calculation that shows how much room this one cancer takes up in Korea's statistics. Women outnumber men among cancer survivors by 345,018. Take thyroid cancer out and the gap disappears.
| Group | All cancer survivors | Thyroid | Everything else |
|---|---|---|---|
| Men | 1,193,944 | 116,344 | 1,077,600 |
| Women | 1,538,962 | 470,948 | 1,068,014 |
| Women − men | +345,018 | +354,604 | −9,586 |
The impression that women get cancer more often does not survive removing this one cancer. What remains is 1,077,600 against 1,068,014 — under 1% apart. That is not a claim that cancer in women matters less; it narrows the answer to what actually produces the difference between the sexes.
Men are not outside this either: 116,344 male survivors, the fourth most common cancer among men.
How not to read these figures
| Common reading | What the figures support |
|---|---|
| “100.2% survival, so it hardly matters” | It is a comparison with the general population, not a headcount — “about the same as someone without it” |
| “Most survivors means most diagnoses” | Annual incidence is within 7.5% of lung cancer. The survivor count is large because people live |
| “Mostly papillary, so it is mild” | 83 anaplastic cases share the name. Survival by type is not in this source |
| “Women get far more cancer” | Remove thyroid cancer and the sexes are level (1.078m against 1.068m) |
| “Not in the national programme, so get an ultrasound privately” | The recommendation says no need without symptoms. With symptoms, see a doctor |
Questions people ask
There is a lump in my neck — what now?
Not screening but a doctor. The recommendation says anyone with “symptoms suggestive of thyroid cancer, such as a palpable lump in the neck, should see a doctor for consultation.” This article reads statistics; it does not diagnose.
Should I add a thyroid ultrasound to my health check?
Without symptoms, the recommendation says no. If it is already included, it is worth agreeing with your doctor in advance what happens if a small nodule appears — the difficulty tends to come after the finding rather than from it.
Why is it so much more common in women?
This material cannot answer that. What is confirmed is the 80.2% share; we could not open an agency source explaining the cause. On the functional side, the Korea Disease Control and Prevention Agency notes that Graves' disease is “four to eight times more common in women,” but that is a different condition and the link to cancer is not established here.
Do men need to think about it?
There are 116,344 male survivors, fourth among cancers in men, and over the last five years male incidence grew twice as fast as female. The screening advice does not differ by sex — symptoms mean a doctor.
Does a large survivor count mean it is increasing?
Not directly. The survivor figure counts everyone diagnosed between 1999 and 2023 who was alive on 1 January 2024 — 25 years of accumulation. Direction comes from incidence trends, set out above.
What about other cancers in women?
Second is breast cancer at 353,411 (23.0%), then colorectal 140,026 (9.1%), stomach 126,460 (8.2%) and cervical 65,438 (4.3%). The top two alone make up 53.6%, and from third place down these are cancers both sexes share. General guidance on reading these indicators is in the cancer prevalence article.
Sources
- National Cancer Information Center — prevalence by cancer type (2023 basis). Source for thyroid cancer first among women at 470,948 (30.6%), breast second at 353,411 (23.0%), colorectal 140,026 (9.1%), stomach 126,460 (8.2%) and cervical 65,438 (4.3%); fourth among men at 116,344 (9.7%); and first overall at 587,292 (21.5%). The Center's overall prevalence page supplies the totals by sex (1,193,944 men, 1,538,962 women) and the definition of the survivor population (diagnosed 1 Jan 1999 to 31 Dec 2023 and alive on 1 Jan 2024).
- National Cancer Information Center — incidence by cancer type (2023) and survival (2019–2023 diagnoses). Source for total incidence of 288,613, thyroid 35,440 (first), lung 32,953, breast 29,871 and stomach 28,943, and for survival of 100.2%, 94.7%, 78.6%, 42.5% and 73.7%.
- National Cancer Information Center — thyroid cancer statistics page (last revised 21 July 2026; 2023 incidence). Source for the age distribution (26.9% in the forties, 22.9% fifties, 20.7% thirties), cases by sex (9,326 men, 26,114 women), the 0.4 : 1 ratio, the crude incidence rate of 69.3 per 100,000, and the table of histological types.
- National Cancer Information Center — analysis of cancer incidence trends. Source for the period changes in thyroid cancer (25.6%, 12.8%, −20.1%, then 3.9% a year through 2021), for stomach cancer at −4.4% and for all cancers in women (+4.8%, −6.2%, +1.7%), and for the note that these are age-standardised rates.
- National Cancer Center thyroid cancer screening recommendation (2015) — posted on the Information Center's seven-cancer screening guidelines board as a PDF (checked August 2026). We could not open the PDF itself; the wording — “those without any symptoms do not need screening by ultrasound” and “anyone with symptoms suggestive of thyroid cancer, such as a palpable lump in the neck, should see a doctor” — is taken from press coverage of its release (October 2015). That is reporting, not an agency text.
- Press reporting — not an agency text. Coverage of a Ministry of Health and Welfare / Korea Central Cancer Registry release (January 2026). Source for the definition of five-year relative survival and for the reading of a figure above 100%. The Center's own pages did not carry that definition.
- Korea Disease Control and Prevention Agency — National Health Information Portal, hyperthyroidism. Source for Graves' disease accounting for 60–80% of hyperthyroidism, being “four to eight times more common in women,” and occurring “mainly between the twenties and forties.” This concerns thyroid function, not cancer.
- Kangbuk Samsung Hospital breast and thyroid centre — a private hospital page reworking National Cancer Information Center data from 2019. Used only for the incidence rankings by age band (thyroid first at 39.0 for ages 15–34 and 92.2 for 35–64; outside the top five past 65), the all-cancer rate of 1,576.6 past 65, and the 2018 case counts by sex (6,727 men, 21,924 women). Being 2019-based, it runs a different year from the rest of this article.
- Our own calculations. Survivors excluding thyroid cancer (1,077,600 men, 1,068,014 women), the 345,018 gap, the 53.6% combined share of the top two cancers in women, the 80.2% female share of thyroid cancer, the “one in 1,443” derived from the 69.3 crude rate, the 70.5% three-band total and its case counts, and the ratio shift (3.26 to 2.80) with the five-year growth rates (+38.6% men, +19.1% women) are ours, computed from the tables above and not figures the agency publishes. Cross-check: 116,344 + 470,948 = 587,292 and 1,193,944 + 1,538,962 = 2,732,906, matching the published totals.
- What we read into it. “The gap between the sexes is explained by this one cancer” is the result of subtracting two tables; no source frames it that way. In the histology table one cell would not reproduce — it prints 95.4% for papillary, while the total gives 94.5% and the carcinoma subtotal gives 95.8%. The page's own body text says 94.5%, so we used that. The trend sentence also attaches “annual average” only to the final interval, leaving the first three ambiguous between annual and whole-period change.
Where to check further
This article goes as far as the agency material allows. What remains is best looked at here.
- Whether to be screened — discuss it with a doctor. The recommendation points away from screening without symptoms, but family history or something palpable changes the question. Statistics cannot settle it.
- The recommendation itself — checked here. The seven-cancer screening guidelines board carries the thyroid entry as a PDF. We could not open it and used quoted press coverage instead.
- Incidence after 2021 — we will update on the next release. The trend analysis runs to 2021 while the rest of this article is 2023-based. The direction in between has not been published.
As of August 2026. Cancer statistics are from the National Cancer Information Center on a 2023 basis (survival on 2019–2023 diagnoses), incidence trends from the same agency's trend analysis through 2021, and the screening position from press coverage of the National Cancer Center's recommendation; subtractions and ratios are marked as our own. This is general information about reading statistics and does not substitute for medical diagnosis or treatment. Decisions about screening and about symptoms belong with a doctor.
