# Carcinoma in situ (CIS)

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

## TL;DR

Cancer cells that fill the lining layer where they started but have not broken through the basement membrane into the tissue beneath. They cannot spread yet, so removal is usually curative; it is 'stage 0'.

## Summary

Staged as Tis, in situ disease is found in breast (ductal and lobular), bladder (flat CIS, which is aggressive and treated with BCG), cervix (CIN 3), skin (Bowen's disease, melanoma in situ), oesophagus and lung (adenocarcinoma in situ). Whether and how fast it would have progressed is often unknowable, which raises overdiagnosis questions in screening. Treatment is local (excision, ablation, intravesical therapy) without systemic chemotherapy, sometimes with radiotherapy or endocrine therapy for breast DCIS.

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: CIS; in situ carcinoma; in situ; Tis; lobular carcinoma in situ; LCIS; stage 0; non-invasive cancer; intraepithelial

## Notes

- How in-situ disease is written in a breast stage. Tis carries the type in brackets: Tis (DCIS), Tis (LCIS), or Tis (Paget's) for Paget disease of the nipple with no underlying carcinoma. A carcinoma in the breast that happens to have Paget disease over the nipple is staged on the carcinoma, with the Paget disease noted.
- In the skin, in situ carcinoma has a name of its own. Squamous cell carcinoma in situ of the skin is called Bowen's disease, is coded D04 rather than C44, and is staged pTis, stage 0, in the UICC system UK skin reports use. It is not the same thing as an actinic keratosis, which sits outside the neoplasm chapter of ICD-10 altogether.

## 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/), [Ductal carcinoma in situ (DCIS)](https://onco.cc/terms/dcis/), [Ducts, lobules and the terminal duct lobular unit](https://onco.cc/terms/terminal-duct-lobular-unit/), [Dysplasia (pre-cancerous change)](https://onco.cc/terms/dysplasia/), [High-grade prostatic intraepithelial neoplasia (HGPIN)](https://onco.cc/terms/high-grade-pin/), [Intraductal carcinoma of the prostate (IDC-P)](https://onco.cc/terms/intraductal-carcinoma-prostate/), [Intravesical therapy (BCG and bladder instillations)](https://onco.cc/terms/intravesical-therapy/), [Keratinocyte cancer (and why 'non-melanoma skin cancer' is being retired)](https://onco.cc/terms/keratinocyte-cancer/), [Rokitansky-Aschoff sinus](https://onco.cc/terms/rokitansky-aschoff-sinus/), [TNM staging](https://onco.cc/terms/tnm-staging/), [Which staging edition a breast report uses: UICC TNM 8, TNM 9 and the AJCC prognostic stage](https://onco.cc/terms/tnm-breast-cancer-editions/)
- cancers: [Bladder & urothelial cancer](https://onco.cc/cancers/urothelial/), [Bowen's disease (squamous cell carcinoma in situ)](https://onco.cc/cancers/bowens-disease/), [Breast cancer (all types)](https://onco.cc/cancers/breast-cancer/), [Carcinoma in situ and dysplasia of the gallbladder](https://onco.cc/cancers/gallbladder-carcinoma-in-situ-and-dysplasia/), [Cervical cancer](https://onco.cc/cancers/cervical/), [Cutaneous squamous cell carcinoma](https://onco.cc/cancers/cutaneous-scc/), [Ductal carcinoma in situ (DCIS)](https://onco.cc/cancers/ductal-carcinoma-in-situ/), [Gallbladder cancer](https://onco.cc/cancers/gallbladder/), [Germ cell neoplasia in situ (GCNIS)](https://onco.cc/cancers/germ-cell-neoplasia-in-situ/), [Lobular carcinoma in situ (LCIS)](https://onco.cc/cancers/lobular-carcinoma-in-situ/), [Melanoma](https://onco.cc/cancers/melanoma/), [Papillary carcinoma of the gallbladder](https://onco.cc/cancers/gallbladder-papillary-carcinoma/), [Skin cancer (all types)](https://onco.cc/cancers/skin-cancer/)
- fronts: [Early Detection & Screening](https://onco.cc/fronts/early-detection/)

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