The cancer most Korean women have lived through is not breast cancer. It is thyroid cancer — and not by a small margin.
⭐⭐ Of the 1,538,962 women counted as prevalent cancer cases in 2023 —
1st, thyroid: 470,948 (30.6%) · 2nd, breast: 353,411 (23.0%)
— National Cancer Information Center, prevalence by cancer site (2023)
⭐ Three in ten women in the prevalence count had thyroid cancer, and first and second together come to 53.6% (our calculation). More than half of them had one of two cancers.
⭐⭐⭐ A 345,000 gender gap, explained by one cancer
Split prevalent cases by sex and women are clearly the larger group.
| Group | All prevalent cases | Thyroid | ⭐ Everything except thyroid |
|---|---|---|---|
| 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" disappears from the statistics once one site is removed. What remains is 1,077,600 against 1,068,014 — a gap of under 1%.
⚠️ Read that carefully. It does not mean women's cancers are somehow minor. It means the question "what creates the sex difference" narrows to a single answer — so the next question naturally becomes "what kind of cancer is this?"
⭐ Four in five thyroid cancer cases are women
| Group | Prevalent cases | Rank within that sex | Share |
|---|---|---|---|
| ⭐ Women | ⭐ 470,948 | ⭐ 1st | 30.6% of women's cases |
| Men | 116,344 | 4th | 9.7% of men's cases |
| Total | 587,292 | 1st | 21.5% of all cases |
⭐ 80.2% are women (our calculation). On the male table it ranks fourth, behind stomach, colorectal and prostate. The same cancer occupies a completely different position depending on sex.
⭐ Thyroid disease in general skews female. Korea's KDCA health portal writes that Graves' disease — which accounts for 60–80% of hyperthyroidism — is “4 to 8 times more common in women” and “most often arises in the 20s to 40s.” ⚠️ But that describes a functional disorder, not cancer, and we could not verify any link between the two. The functional side is covered in our thyroid warning signs article.
⭐⭐ Why so many — separate incidence from prevalence
A common misreading lives here: ranking first in prevalence does not mean "the cancer most people get."
| Site | New in 2023 | Prevalent | ⭐ Ratio (our calculation) | 5-year relative survival |
|---|---|---|---|---|
| ⭐ Thyroid | 35,440 | 587,292 | ⭐ 16.6× | 100.2% |
| ⚠️ Lung | 32,953 | 141,143 | ⚠️ 4.3× | ⚠️ 42.5% |
| Breast | 29,871 | 354,699 | 11.9× | 94.7% |
| Stomach | 28,943 | 366,717 | 12.7× | 78.6% |
| All cancers | 288,613 | 2,732,906 | 9.5× | 73.7% |
⭐⭐⭐ Thyroid and lung cancer produce almost the same number of new cases a year — 35,440 against 32,953, a 7.5% gap.
Yet the number of people alive differs 4.16-fold: 587,292 against 141,143.
⭐ If the same number enters and a different number accumulates, the difference is how long people stay.
⭐ Thyroid cancer's 5-year relative survival is 100.2%, the highest site in the source, and its 16.6× ratio is 1.7 times the all-cancer average of 9.5×.
⭐ The word “relative” in the name is the answer — this is a comparison, not a plain proportion.
“Five-year relative survival (the probability that a cancer patient survives five years, compared with the general population)”
“A relative survival of 100% means survival equal to the general population; thyroid cancer exceeding 100% means that, going by the number alone, patients outlive the general population.”
— Korean news report (20 January 2026). ⚠️ A news source, not agency source text.
⭐⭐ So 100.2% does not mean “100 out of 100 survive” — it is closer to “about the same as comparable people without the diagnosis.” ⚠️⚠️ But note the report's own hedge, “going by the number alone”: why it comes out higher is not explained. So do not carry this over as “a cancer it's fine to get.” How to read these indicators generally is set out in the prevalence article.
⭐⭐ Who gets it — the 40s lead
Prevalence is 25 years of cases stacked up, so it cannot tell you who is being diagnosed now. For that you need one year of incidence. Here are the 35,440 thyroid cancer cases of 2023 broken out by age band.
| Age band | Share of cases | ⭐ Cases (our calculation) |
|---|---|---|
| ⭐ 40s | ⭐ 26.9% (largest) | about 9,533 |
| 50s | 22.9% | about 8,116 |
| 30s | 20.7% | about 7,336 |
| ⭐ Three bands combined | ⭐ 70.5% | about 24,985 |
⚠️ Only the three shares are printed in the source. The 70.5% total and the case counts are ours, and the page does not say how the remaining 29.5% is spread across other ages.
⭐ The sex ratio shows up in incidence too. The source gives a male-to-female ratio of 0.4 : 1, with 9,326 cases in men and 26,114 in women. ⭐ Checking: 9,326 + 26,114 = 35,440, exactly the printed total.
⭐⭐⭐ And here the two halves of this article meet.
By incidence, thyroid cancer is the second most common cancer in women (breast cancer leads with 29,871 cases). By prevalence it is first — 470,948 women, 30.6%, against 353,411 for breast cancer.
⭐ Our calculation: people living with the disease per year of new cases — 18.0× for thyroid, 11.8× for breast.
→ It trails by 3,757 cases in a single year and leads by 117,537 in the accumulated count. That is why the ranking flips.
⭐⭐⭐ Is it still rising? It fell, then turned back up
587,292 people living with the disease is 25 years stacked up, which says nothing about direction. This article long carried the note that we could not obtain a year-by-year incidence trend. We have now found one.
| Period | Change in age-standardised incidence | Direction |
|---|---|---|
| 1999–2008 | 26.1% | rising |
| 2008–2012 | 13.2% | rising, at half the pace |
| ⭐ 2012–2015 | ⭐ 18.3% | ⭐ falling — the only such period |
| ⚠️ 2015–2019 | ⚠️ 4.2% a year | ⚠️ rising again |
⚠️⚠️ Three things to be careful about when reading this table.
- ⚠️ The unit is ambiguous. The source attaches “annual average” only to the last period and not to the first three. Set beside the other cancers in the same paragraph (breast 4.3%, prostate 7.3%), reading them all as annual rates is natural — but the source does not say so. So our table marks only the last row as an annual figure.
- ⚠️ Why it fell and then rose is not in the source. We have not supplied a reason.
- ⚠️ It stops at 2019. Every other figure in this article is 2023, so the years are four apart.
⭐ What is clear is that neither “still climbing steeply” nor “now falling” describes it. The shape is one break, then a gentler climb.
⭐⭐ Thyroid cancer is absent from the top five after 65
We said above that 70.5% of cases fall between the 30s and the 50s. A ranking cut by age group confirms it from another angle (2019 data).
| Age group | Highest incidence rate | Where thyroid sits |
|---|---|---|
| 0–14 | Leukaemia (4.4) | 4th (0.4) |
| ⭐ 15–34 | ⭐ Thyroid (39.0) | ⭐ 1st |
| ⭐ 35–64 | ⭐ Thyroid (92.2) | ⭐ 1st |
| ⚠️ 65 and over | Lung (269.7) | ⚠️⚠️ not in the top five |
⭐⭐⭐ First across two consecutive age bands from 15 to 64, then gone from the top five after 65.
The top five over 65 are lung (269.7), colorectal (205.3), stomach (201.4), prostate (168.0) and liver (105.0).
⚠️ “Gone from the list” does not mean “does not happen” — other cancers rise far faster at that age. The same source puts all-cancer incidence over 65 at 1,576.6 per 100,000.
⭐ This locks in with the first half of the article. Across all cancers, 51.5% of people living with cancer are 65 or older — yet thyroid cancer sits outside the top ranks at that age. First in prevalence, and not a cancer of old age: that is the shape of it.
⭐⭐ The sex gap is narrowing (our calculation)
That the disease skews female we established above. But placing the 2018 and 2023 counts side by side shows a direction.
| Year | Men | Women | ⭐ Women ÷ men |
|---|---|---|---|
| 2018 | 6,727 | 21,924 | 3.26× |
| 2023 | 9,326 | 26,114 | ⭐ 2.80× |
| ⭐ Growth over five years | ⭐ +38.6% | +19.1% | — |
⭐⭐ Cases in men grew at twice the rate (+38.6% against +19.1%, our calculation), pulling the ratio down from 3.26× to 2.80×. ⚠️ Neither source explains why.
⚠️⚠️ And one sentence in the source contradicts its own numbers.
It gives the international comparison as “about 1:5 in Japan, about 1:3 in the United States,” and then says “the female share in Korea is higher than abroad.”
⭐ But the Korean 2018 ratio printed in the same paragraph is 0.3:1 — women about 3.26× men.
→ Japan 5× > Korea 3.26× > US 3×. ⚠️ “Higher than abroad” does not hold against Japan, at least. So this article does not use the international comparison as a conclusion.
⭐⭐⭐ Nine in ten are papillary — but one cell of the table does not add up
Thyroid cancer is not one thing. The source prints a breakdown by histologic type, so we reproduce it.
| Histologic type | Cases | Printed share | ⭐ Recomputed on the total |
|---|---|---|---|
| Carcinoma | 34,959 | 98.6% | 98.6% ✅ |
| ⭐ Papillary | 33,498 | ⚠️⚠️ 95.4% | ⚠️ 94.5% — mismatch |
| Follicular | 1,016 | 2.9% | 2.9% ✅ |
| Medullary | 148 | 0.4% | 0.4% ✅ |
| Anaplastic | 83 | 0.2% | 0.2% ✅ |
| Unspecified malignant neoplasm | 477 | 1.3% | 1.3% ✅ |
| Total | 35,440 | 100.0% | — |
⚠️⚠️⚠️ Checking the arithmetic, one cell fails.
Every other cell matches the 35,440 total — follicular 1,016÷35,440 = 2.9%, medullary 148÷35,440 = 0.4%, and so on.
But papillary alone works out to 33,498÷35,440 = 94.5%, while the table prints 95.4%.
⭐ Switching the denominator to carcinoma (34,959) gives 95.8%, so no denominator produces 95.4%.
⚠️ The body text on the same page says 94.5%. We use 94.5% — but we could not determine why the table differs.
⭐ The counts themselves reconcile perfectly. 33,498 + 1,016 + 148 + 83 + 174 + 40 = 34,959 (the carcinoma subtotal), and adding sarcoma 0 + other specified 4 + unspecified 477 gives 35,440. Only one percentage cell is off.
⚠️ One phrase in the body text also blurs the denominator. It reads “among carcinomas, papillary accounts for 94.5%” — but 94.5% is measured against the total, and against carcinomas it would be 95.8%. ⭐ The accurate reading is “94.5% of all thyroid cancers are papillary.”
⚠️⚠️ Do not read this table as “so most of it is the mild kind.” 83 anaplastic cases sit under the same name and behave nothing like the rest. ⚠️ Survival and prognosis by type are not in this source, so this article gives shares only.
⚠️ And thyroid cancer is not in the national screening programme
Despite ranking first among women, it is not on the list of cancers screened free of charge by the state. The covered sites and intervals are in the national cancer screening guide.
⚠️ Why it is absent we could not verify — we were unable to open the documents that set the screening list. So we state the fact and not a reason: it is not on the list, and being off the list means neither "ignore it" nor "get it done privately." ⭐ Whether to be screened is a conversation to have with a doctor.
How to read these statistics
| Don't read it as | Read it as |
|---|---|
| ⚠️ “women get far more cancer” | ⭐ excluding thyroid, the sexes are level (1.078M vs 1.068M) |
| ⚠️ “first in prevalence = most diagnosed” | incidence is within 7.5% of lung cancer — prevalence is high because people live |
| ⚠️ “100.2% survival, so it's fine to get” | ⭐ a comparison with the general population — “about the same,” not “everyone lives” |
| ⚠️ “men needn't think about it” | 116,344 men — 4th among male cases |
| ⚠️ “not screened, so not important” | ⚠️ we do not know why it is excluded — decide with a doctor |
Questions that remain
Why is it so much more common in women?
⚠️ These sources cannot answer that. What we verified is the 80.2% share, nothing more; we could not open agency source text explaining the cause. 🆕 A private hospital page offers the hypothesis that “women undergo health screening more often than men,” ⚠️ but that sentence is itself hedged as a supposition and carries no supporting evidence. ⭐ On the functional side, the KDCA writes that Graves' disease is “4 to 8 times more common in women” — ⚠️ but cancer and functional disorders are different conditions and the link was not verified.
Does high prevalence mean it is rising?
⚠️ Not directly. Prevalence counts everyone diagnosed between 1999 and 2023 who was alive on 1 January 2024 — 25 years of accumulation. Judging whether it is rising now requires incidence trends by year, and ⚠️ we did not obtain those.
What if I can feel a lump in my neck?
This article is about reading statistics, not diagnosing symptoms. Thyroid symptoms and test values are covered in thyroid warning signs. If you can feel something, settle it with a doctor, not a statistic.
Should men get checked?
⚠️ This article neither recommends nor discourages testing. The verified facts only: 116,344 men, 4th among male cancers, and thyroid cancer is not in the national screening list for either sex. Decide with a doctor.
What about the other cancers in women?
Second is breast cancer, 353,411 (23.0%), then colorectal 140,026 (9.1%), stomach 126,460 (8.2%) and cervical 65,438 (4.3%). ⭐ First and second alone make 53.6%, and from third down they are cancers both sexes share. Other axes of women's health are covered in bone health, menopause and anaemia.
Three in ten women in Korea's cancer prevalence count had thyroid cancer. And the 345,000 gap between women and men vanishes once that one cancer is removed — a single subtraction shows what the sentence "women get more cancer" was actually pointing at.
Sources
- ⭐ National Cancer Information Center (Korea) — Prevalence by cancer site (2023). ⭐⭐ Source for women: 1st thyroid 470,948 (30.6%), 2nd breast 353,411 (23.0%), 3rd colorectal 140,026 (9.1%), 4th stomach 126,460 (8.2%), 5th cervical 65,438 (4.3%); men: 4th thyroid 116,344 (9.7%); all: 1st thyroid 587,292 (21.5%).
- National Cancer Information Center — Cancer prevalence (2023). Source for the sex split (1,193,944 men, 1,538,962 women), the total of 2,732,906, and the basis (diagnosed 1999-01-01 to 2023-12-31, alive on 2024-01-01).
- National Cancer Information Center — Incidence by cancer site (2023). Source for 288,613 new cases, thyroid 35,440 (1st, 12.3%), lung 32,953, breast 29,871, stomach 28,943.
- National Cancer Information Center — Cancer survival (2019–2023 diagnoses). Source for thyroid 100.2%, breast 94.7%, stomach 78.6%, lung 42.5%, all cancers 73.7%.
- ⚠️ News report (not agency source text) — Korean coverage of the statistics released by the Ministry of Health and Welfare and the Korea Central Cancer Registry (National Cancer Center), 20 January 2026. Source for “five-year relative survival (the probability that a cancer patient survives five years, compared with the general population)” and “exceeding 100% means that, going by the number alone, patients outlive the general population.”
- Korea Disease Control and Prevention Agency — National Health Information Portal, hyperthyroidism. Source for Graves' disease accounting for 60–80% of hyperthyroidism, “4 to 8 times more common in women,” and “most often arises in the 20s to 40s.” ⚠️ This concerns a functional disorder, not cancer.
- ⭐⭐ National Cancer Information Center — “Thyroid cancer” › related statistics (page last updated 21 July 2026; 2023 incidence). Source for the age bands (40s 26.9%, 50s 22.9%, 30s 20.7%), the cases by sex (9,326 men — 6th among cancers in men; 26,114 women — 2nd among cancers in women), the 0.4 : 1 sex ratio, the crude incidence rate of 69.3 per 100,000, and the histologic-type table.
- ⚠️ Kangbuk Samsung Hospital, Breast & Thyroid Cancer Center — “Thyroid cancer › Statistics” (a private hospital page restating 2019 National Cancer Information Center data). Source for the period-by-period change in age-standardised incidence (26.1%, 13.2%, 18.3%, 4.2% a year), the rankings by age group (thyroid 1st at 39.0 for 15–34 and 92.2 for 35–64; outside the top five over 65), all-cancer incidence over 65 of 1,576.6, the 2018 counts by sex (6,727 men, 21,924 women), and the international ratios (Japan 1:5, US 1:3). ⚠️⚠️ Not agency source text, and dated 2019 — four years apart from the 2023 figures used elsewhere here.
- ⭐ Our own calculation. The thyroid-excluded totals (1,077,600 men; 1,068,014 women), the 345,018 gap, the 53.6% first-plus-second share, the 80.2% female share of thyroid cases, and the prevalence-to-incidence ratios are computed by us, not printed in the source. ⭐ Checks: thyroid 116,344 + 470,948 = 587,292, and 1,193,944 + 1,538,962 = 2,732,906 — both match the published totals exactly.
What we could not verify
- ⚠️⚠️ Why it is so much more common in women. No agency source text explaining the cause could be opened, which is why the body gives the share and no interpretation. ⚠️ Nor is there any source connecting the sex ratio in thyroid function disorders (Graves', 4–8×) to the sex ratio in thyroid cancer.
- ⚠️⚠️ Why thyroid cancer is excluded from national screening. The documents that set the screening list were not accessible, so we state the fact without a reason.
- ⚠️ The agency's own definition and formula for relative survival. The meaning came from a news report; the National Cancer Information Center page still has none, and how expected survival is derived was not obtained.
- ⚠️⚠️ Why it exceeds 100. The report says only “going by the number alone”; the body offers no cause.
- 🆕 ⚠️⚠️ Why the papillary percentage differs. The table prints 95.4%, but 94.5% on the total and 95.8% on carcinomas — neither denominator reproduces it. The body text on the same page says 94.5%. We followed the body text and could not establish the reason.
- 🆕 ⚠️⚠️ The unit of the incidence change figures. The source attaches “annual average” to the last period only, so we could not establish whether the first three are annual rates or total change over the period.
- 🆕 ⚠️⚠️ The trend after 2019. The data we found stops at 2019, so the direction through 2023 remains unknown.
- 🆕 ⚠️ Why incidence fell in 2012–2015 and rose again. No reason is given in the source, so we gave none.
- 🆕 ⚠️ Why male cases are growing faster than female ones. Neither source addresses it.
- 🆕 ⚠️⚠️ The international comparison sentence. The source says “the female share in Korea is higher than abroad,” but by the numbers in the same paragraph Japan (5×) is higher than Korea (3.26×). We could not resolve which is right and did not use it as a conclusion.
- 🆕 ⚠️ “Half the population has thyroid nodules, 5% of which are cancer.” This widely repeated claim appears in the same source hedged as an estimate, with no citation. We left it out.
- 🆕 Survival and prognosis by histologic type. Only shares are published, so we did not extend the table into any claim about outcomes.
- ⚠️ Age distribution of people living with the disease. 🆕 We now have the age bands for incidence (40s 26.9% and so on), but which ages the prevalent cases cluster in is still unverified; only the all-cancer figure (51.5% aged 65+) is confirmed. ⚠️ Incidence age and prevalence age are not the same thing — prevalence covers 25 accumulated years, so it skews older.
- 🆕 The remaining 29.5% of cases by age. The source lists only the top three bands, so the shares for under 30 and 60+ are unknown.
- Distribution by stage, and treatment approaches — not in these sources.
- Mortality statistics. This article uses prevalence, incidence and survival only.
- ⚠️ The cancer statistics come from a single institution. All four pages are the National Cancer Information Center, with no cross-check against another body.
As of July 2026. Cancer statistics come from the National Cancer Information Center's 2023 data (survival on 2019–2023 diagnoses) and the thyroid-function material from the KDCA National Health Information Portal; the subtractions and ratios are our own, marked as such in the body. For the indicators generally see the prevalence article; for symptoms and test values, thyroid warning signs. This is general information about reading statistics and does not replace medical diagnosis or treatment. Discuss screening and symptoms with a doctor.
