# Why nobody knows how many skin cancers there are: the counting rule behind every figure

Source: https://onco.cc/terms/keratinocyte-cancer-counting/  
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## TL;DR

Cancer registries were never built to count a cancer that people get several of. Britain's registries long recorded only the first basal cell carcinoma and the first squamous cell carcinoma in a person's lifetime, and the headline 'cancer in the UK' figure leaves these cancers out altogether. Every number on these pages is a floor, not a count.

## Summary

The rule came first. In 1999 the UK and Ireland Association of Cancer Registries decided that, because of the difficulty of registering multiple pathology reports accurately, only the first basal cell carcinoma or squamous cell carcinoma per patient would be reported (quoted in Venables 2019). That is one registration per person per lifetime for each of the two types, whatever happens afterwards. Since people who get one keratinocyte cancer very often get several, the effect is large and one-directional.

How large has now been measured three times, each by comparing the old rule against counting the first of each type per person per year instead. Over England in 2013 to 2015, the annual method found 410,716 basal cell carcinomas against 268,565 on the old rule, 53 percent more, and 104,529 squamous cell carcinomas against 76,977, 36 percent more; 51 percent more keratinocyte cancers in all, and the authors judged that even this was still 5 to 11 percent short of the true tumour count (Venables 2019). Over 2013 to 2018 the gap was 59.2 percent for basal cell carcinoma and 37.2 percent for squamous cell carcinoma, and the residual shortfall was about 14 basal cell carcinomas and 2 squamous cell carcinomas per 100 patients (Kwiatkowska 2021). Over 2013 to 2022 it was 67 percent and 42 percent (Mistry 2026). The direction is always the same: the more carefully anybody counts, the more there turn out to be.

The four UK nations do not do the same thing, so their figures are not comparable with each other. England registers the first of each type per person and imputes the rest from pathology records, publishing on the annual basis. Scotland collects only the first occurrence of a basal cell carcinoma, in its own words 'because they are so common', but registers every squamous cell carcinoma manually (Public Health Scotland, September 2025; Venables 2019). Wales moved to the annual method from 2016 data and is the most explicit about it; on that basis non-melanoma skin cancer was 40 percent of all cancer cases in Wales in 2020, 11,792 first occurrences against 17,461 of every other cancer combined (Public Health Wales, May 2024). Northern Ireland publishes about 3,852 cases a year for 2018 to 2022.

And then the whole group is taken out of the headline. The Office for National Statistics defines all cancers as ICD-10 C00 to C97 excluding C44, stating that it has been advised 'that non-melanoma skin cancer (NMSC) is greatly under-registered' and that the exclusion exists 'to ensure that the reported figures are meaningful'; its bulletins add that the available figures 'are known to be underestimates and unreliable for comparison purposes' because recording policies have varied between registries. So when a British source says there are just over 400,000 new cancers a year in the UK, the commonest cancer of all is not in that number: around 156,000 non-melanoma skin cancers are counted separately (Cancer Research UK), and the research estimate on the annual method is 234,861 a year across the UK for 2016 to 2018 (Kwiatkowska 2021).

None of this is a reason to distrust the figures. It is a reason to read them as the floor of a range. Two practical rules follow. A rising trend in these statistics may be a rising disease, a changing counting rule, or both, and a reader should check which is being compared. And a comparison between England and another country is very often a comparison of counting methods: the NDRS notes that English rates can look alarmingly high beside other countries' simply because other countries still count only the first tumour.

## Fields

- Kind: Term
- Last checked: 2026-09-25
- Also known as: skin cancer under-registration; non-melanoma skin cancer registration; NMSC under-registration; first per person per annum; 1st PPPA; PPPA; first tumour per patient; UKIACR counting rule; C44 excluded; all cancers excluding non-melanoma skin cancer; keratinocyte cancer incidence caveat; skin cancer statistics caveat

## Notes

- The figures this term qualifies, with their methods named. On the lifetime-first method Cancer Research UK gives around 156,000 new non-melanoma skin cancers a year in the UK, against 403,601 of all other cancers combined, and 1,200 deaths a year. On the annual method the research estimate is 234,861 a year across the UK for 2016 to 2018, 184,280 basal cell and 50,582 squamous cell carcinomas (Kwiatkowska 2021). In England in 2022, age-standardised rates on the annual method were 295 per 100,000 person-years for basal cell carcinoma and 102 for squamous cell carcinoma (Mistry 2026). Registry counts in England for 2019 were 282.36 per 100,000 person-years for basal cell carcinoma and 85.24 for squamous cell carcinoma (van Bodegraven 2023).
- Why this is not simply a data-quality complaint. Under-registration has consequences a patient can feel. Services are commissioned on registered numbers; dermatology and Mohs capacity is planned on them; and a cancer that is officially rare enough to leave out of the national total competes badly for attention against cancers that are in it. The same registries that cannot count these tumours can count melanoma precisely, which is part of why melanoma has more research behind it.
- The coding system cannot see the distinction that decides treatment. Registries code morphology in ICD-O, and ICD-O gives micronodular basal cell carcinoma no code of its own, filing it as a related term under 8097/3 alongside nodular, which is a low-risk pattern; sclerosing and morphoeic share 8092/3 with infiltrating. So registry data can separate basal cell from squamous cell carcinoma but cannot reliably separate the high-risk growth patterns from the low-risk ones. Any statement about how many high-risk basal cell carcinomas there are in Britain therefore rests on reading reports rather than on counting codes.
- Mortality is counted differently again and is rising. Deaths are published for non-melanoma skin cancer as a single category, which may include rare tumours such as Merkel cell carcinoma as well as squamous cell carcinoma (Kwiatkowska 2021). In England that age-standardised mortality rate rose significantly from 2013, by about 4.0 percent a year, and roughly twice as fast in men as in women (Mistry 2026). A cancer group whose incidence is undercounted and whose mortality is rising is not the harmless thing the exclusion from the national total implies.

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Cancer_registry
- Venables et al., British Journal of Dermatology 2019;181(3):474 to 482: epidemiology of basal and cutaneous squamous cell carcinoma in the UK 2013 to 2015, a cohort study (the paper that introduced the first-per-person-per-annum count): https://doi.org/10.1111/bjd.17873
- Kwiatkowska et al., Skin Health and Disease 2021;1(4):e61: an updated report on the incidence and epidemiological trends of keratinocyte cancers in the United Kingdom 2013 to 2018: https://doi.org/10.1002/ski2.61
- Mistry, Levell, Karponis, Wakkee, Whiteman, Proby and Venables, British Journal of Dermatology 2026: trends in keratinocyte cancers in England 2013 to 2022, basal cell carcinoma incidence, cutaneous squamous cell carcinoma incidence and non-melanoma skin cancer mortality: https://doi.org/10.1093/bjd/ljag315
- Office for National Statistics: cancer registration statistics quality and methodology information (the statement that non-melanoma skin cancer is greatly under-registered, and that all-cancer figures are ICD-10 C00 to C97 excluding C44), last revised 23 February 2016: https://www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/conditionsanddiseases/methodologies/cancerregistrationstatisticsqmi
- Office for National Statistics: cancer registration statistics, England, 2017 (data quality section, the exclusion of non-melanoma skin cancer from all-cancer counts), released 26 April 2019: https://www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/conditionsanddiseases/bulletins/cancerregistrationstatisticsengland/2017
- Public Health Scotland: cancer incidence in Scotland to December 2023, published 30 September 2025 (only the first occurrence of a basal cell carcinoma is collected in Scotland): https://publichealthscotland.scot/publications/cancer-incidence-in-scotland/cancer-incidence-in-scotland-to-december-2023/
- Public Health Wales: non-melanoma skin cancer incidence in Wales, published 30 May 2024 (first per person per annum counting; non-melanoma skin cancer was 40 percent of all cancer cases in Wales in 2020): https://phw.nhs.wales/reports/non-melanoma-skin-cancer-incidence-in-wales/
- Cancer Research UK: non-melanoma skin cancer incidence statistics (UK): https://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/non-melanoma-skin-cancer/incidence
- Cancer Research UK: all cancers combined incidence statistics (UK): https://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/all-cancers-combined/incidence
- van Bodegraven et al., British Journal of Dermatology 2023;188(6):777 to 784: 'Get Data Out' Skin, national cancer registry incidence and survival rates for all registered skin tumour groups for 2013 to 2019 in England: https://doi.org/10.1093/bjd/ljad033

## Connected records

- technologies: [Cancer registries and population surveillance](https://onco.cc/technologies/cancer-registries-surveillance/)
- pathways: [Field cancerisation](https://onco.cc/pathways/field-cancerisation/)
- terms: [Actinic keratosis (solar keratosis): sun damage, not cancer](https://onco.cc/terms/actinic-keratosis/), [Incidence versus prevalence](https://onco.cc/terms/incidence-vs-prevalence/), [Keratinocyte cancer (and why 'non-melanoma skin cancer' is being retired)](https://onco.cc/terms/keratinocyte-cancer/)
- cancers: [Basal cell carcinoma](https://onco.cc/cancers/basal-cell-carcinoma/), [Bowen's disease (squamous cell carcinoma in situ)](https://onco.cc/cancers/bowens-disease/), [Cutaneous squamous cell carcinoma](https://onco.cc/cancers/cutaneous-scc/), [Melanoma](https://onco.cc/cancers/melanoma/), [Merkel cell carcinoma](https://onco.cc/cancers/merkel-cell-carcinoma/), [Skin cancer (all types)](https://onco.cc/cancers/skin-cancer/)
- fronts: [Diagnostics & Biomarkers](https://onco.cc/fronts/diagnostics/)

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