# In situ

Source: https://onco.cc/terms/in-situ/  
OnCo record `in-situ` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Latin for 'in place': abnormal cells that look like cancer but have not yet broken through the layer they started in. Stage 0. Not yet able to spread, and usually curable by removing it.

## Summary

Ductal carcinoma in situ (DCIS) of the breast, cervical intraepithelial neoplasia found by smear tests, and high-grade dysplasia in Barrett's oesophagus or colon polyps are all in situ or precancerous lesions; the basement membrane beneath the epithelium is still intact, so the cells have no access to blood or lymph vessels. Screening programmes detect many such lesions, which is both their strength (removing them prevents cancer) and their difficulty (many would never have progressed, so some treatment is overtreatment). Trials such as LORIS and COMET test whether low-risk DCIS can safely be watched rather than removed.

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: carcinoma in situ; in-situ; ductal carcinoma in situ; DCIS; stage 0; pre-invasive; preinvasive; pre-cancer; precancer; precancerous; pre-cancerous; premalignant; pre-malignant; dysplasia; high-grade dysplasia; precancers

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Carcinoma_in_situ
- Wikipedia: https://en.wikipedia.org/wiki/Carcinoma_in_situ

## Connected records

- terms: [Actinic keratosis (solar keratosis): sun damage, not cancer](https://onco.cc/terms/actinic-keratosis/), [Benign versus malignant](https://onco.cc/terms/benign-vs-malignant/), [Invasive](https://onco.cc/terms/invasive-cancer/), [Lesion](https://onco.cc/terms/lesion/), [Screening](https://onco.cc/terms/screening/), [Stage](https://onco.cc/terms/cancer-stage/)
- pathways: [Field cancerisation](https://onco.cc/pathways/field-cancerisation/)
- cancers: [Bowen's disease (squamous cell carcinoma in situ)](https://onco.cc/cancers/bowens-disease/), [Ductal carcinoma in situ (DCIS)](https://onco.cc/cancers/ductal-carcinoma-in-situ/)

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JSON: https://onco.cc/api/v1/entities/in-situ.json