# What is not a second cancer: recurrence, metastasis and field cancerisation

Source: https://onco.cc/terms/rejuv-second-what-is-not-a-second-cancer/  
OnCo record `rejuv-second-what-is-not-a-second-cancer` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Four different things get called the same thing in conversation and in the news, and the difference changes what the news means. A second cancer is a new disease with its own stage and its own chance of cure. A recurrence is the first one back. A metastasis is the first one somewhere else. Field cancerisation is a whole area of tissue that was already changed before any of them.

## Summary

Why the distinction is the first question to ask. When something new is found in a person who has had cancer, the answer to "is this the old one or a new one" decides the stage, the treatment and the outlook. A new, early, localised cancer in someone treated five years ago may be curable; the same tumour called a recurrence of a treated cancer is a different situation entirely. Pathology, imaging and sometimes molecular comparison of the two tumours decide it, and it is a reasonable question to ask the team directly: is this a new primary, or the old one.

A second primary cancer. A new cancer, arising from different cells, with a different histology or in a different organ, counted by cancer registries as a separate diagnosis under published multiple-primary rules. It is staged on its own, treated on its own and has its own prognosis. This file is about these.

A recurrence. The first cancer returning, locally, regionally or at a distance, after a period when it could not be detected. It carries the identity of the first cancer, and a late recurrence of a hormone-receptor-positive breast cancer fifteen years on is still that breast cancer. The corpus glossary entries on recurrence and on late recurrence, linked below, cover this.

A metastasis. The first cancer growing somewhere else. Breast cancer cells in the lung are breast cancer in the lung, not lung cancer, and they are treated as breast cancer. This is the confusion that appears most often in news reporting about public figures.

Field cancerisation. The idea, described by Slaughter in 1953 from oral squamous epithelium, that a whole region of tissue exposed to a carcinogen is altered before any tumour appears, so that multiple cancers arise independently from the same changed field. It explains why a head and neck cancer caused by smoking and alcohol is followed by another one in the same mucosa, and why one sun-damaged patch of skin produces a succession of keratinocyte cancers. The resulting second tumours are genuinely new primaries, but their cause is the shared field rather than the treatment. The corpus record on field cancerisation, linked below, covers the biology.

The hard case: the other side of a paired organ. A cancer in the opposite breast, kidney, lung or testis is a new primary, not a recurrence, and is usually treated as one. The numbers are instructive. Among 29,515 American men diagnosed with testicular cancer between 1973 and 2001, 175 presented with a synchronous cancer in the other testis and 287 developed one later, an observed-to-expected ratio of 12.4 (95% CI 11.0 to 13.9) and a 15-year cumulative risk of 1.9 per cent (1.7 to 2.1). Ten-year overall survival after a metachronous contralateral testicular cancer was 93 per cent (88 to 96), and after a synchronous one 85 per cent (78 to 90). A twelvefold relative risk and a 1.9 per cent absolute risk are the same finding stated two ways, and the survival figures are why that study supported not biopsying the other testis routinely.

The practical consequence. If a report says someone's cancer has "spread to the brain", that is metastasis. If it says they have "developed brain cancer", those are different claims and usually one of them is wrong. If a survivor is told they have a second cancer, the right next questions are which organ it started in, what stage it is, and whether it is being treated with the aim of cure, because the answers are frequently better than the phrase suggests.

## Fields

- Kind: Term
- Last checked: 2026-10-02
- Also known as: Second cancer versus recurrence; New primary or metastasis; Contralateral cancer
- Tags: rejuvenation; survivorship; second-cancers; late-effects

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Metastasis
- Slaughter et al., Field cancerization in oral stratified squamous epithelium: clinical implications of multicentric origin (Cancer 1953): https://doi.org/10.1002/1097-0142(195309)6:5<963::aid-cncr2820060515>3.0.co;2-q
- Fossa et al., Risk of contralateral testicular cancer: a population-based study of 29,515 US men (JNCI 2005): https://doi.org/10.1093/jnci/dji185
- Travis et al., Second cancers among 40,576 testicular cancer patients: focus on long-term survivors (JNCI 2005): https://doi.org/10.1093/jnci/dji278
- NCI: Survivorship, late effects of cancer treatment: https://www.cancer.gov/about-cancer/coping/survivorship

## Connected records

- terms: [Late recurrence](https://onco.cc/terms/late-recurrence/), [Metastasis](https://onco.cc/terms/metastasis/), [Recurrence and relapse](https://onco.cc/terms/relapse-recurrence/), [Screening survivors: where the UK, American and European answers differ](https://onco.cc/terms/rejuv-second-screening-after-treatment-compared/), [Second cancers after radiotherapy](https://onco.cc/terms/second-cancers-after-radiotherapy/), [Second cancers after treatment: what the risk is, and what is done about it](https://onco.cc/terms/rejuv-second-cancers-overview/), [Secondary malignancy (therapy-related cancer)](https://onco.cc/terms/secondary-malignancy/), [Skin cancer after cancer treatment](https://onco.cc/terms/second-primary-skin-cancer-after-cancer-treatment/), [The next skin cancer: second primaries after a keratinocyte cancer](https://onco.cc/terms/second-primary-skin-cancer/)
- cancers: [Breast cancer (all types)](https://onco.cc/cancers/breast-cancer/), [Head and neck squamous cell carcinoma](https://onco.cc/cancers/head-and-neck/), [Seminoma](https://onco.cc/cancers/seminoma/), [Testicular germ cell tumours](https://onco.cc/cancers/testicular/)
- fronts: [Recovery & Rejuvenation](https://onco.cc/fronts/rejuvenation/), [Supportive Care & Survivorship](https://onco.cc/fronts/supportive-care/)
- technologies: [Survivorship care and late-effects surveillance](https://onco.cc/technologies/survivorship-care-plan/)
- pathways: [Field cancerisation](https://onco.cc/pathways/field-cancerisation/)
- bottlenecks: [Knowledge reaches practice too slowly](https://onco.cc/bottlenecks/b-knowledge-diffusion/), [Misinformation and unproven therapies](https://onco.cc/bottlenecks/b-misinformation/), [Survivorship and late effects are neglected](https://onco.cc/bottlenecks/b-survivorship/)

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