# Tumour differentiation (well / moderately / poorly differentiated)

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

## TL;DR

How much the cancer cells still resemble the normal tissue they came from. Well-differentiated tumours look almost normal and tend to grow slowly; poorly differentiated ones have lost their identity and behave aggressively. It is the basis of grade.

## Summary

Pathologists assign differentiation from gland formation, nuclear appearance and mitotic rate; it underlies grading systems such as Gleason (prostate), Nottingham (breast) and WHO grade for neuroendocrine tumours (well-differentiated NETs versus poorly differentiated neuroendocrine carcinomas, which are treated like small-cell cancer). Well-differentiated mucosal gastric cancers qualify for endoscopic resection; poorly differentiated thyroid cancer loses iodine uptake. Dedifferentiation over time (liposarcoma, thyroid, prostate to neuroendocrine) marks transformation to a more aggressive state.

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: well-differentiated; well differentiated; moderately differentiated; poorly differentiated; poorly-differentiated; undifferentiated; dedifferentiated; differentiated thyroid cancer; differentiated

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Grading_(tumors)
- Wikipedia: https://en.wikipedia.org/wiki/Grading_(tumors)

## Connected records

- terms: [Acinar adenocarcinoma of the prostate](https://onco.cc/terms/prostate-acinar-adenocarcinoma/), [Adenocarcinoma](https://onco.cc/terms/adenocarcinoma/), [Cribriform growth pattern in prostate cancer](https://onco.cc/terms/cribriform-prostate-cancer/), [Dysplasia (pre-cancerous change)](https://onco.cc/terms/dysplasia/), [Gleason score / Grade Group](https://onco.cc/terms/gleason-grade-group/), [Grade versus stage](https://onco.cc/terms/grade-vs-stage/), [Histology](https://onco.cc/terms/histology/), [Keratoacanthoma: the tumour that may be a squamous cell carcinoma](https://onco.cc/terms/keratoacanthoma/), [Nottingham grade (breast cancer grade 1, 2 and 3)](https://onco.cc/terms/nottingham-grade/), [The growth pattern on a basal cell carcinoma report: nodular, superficial, infiltrative, basosquamous](https://onco.cc/terms/bcc-growth-pattern/), [The subtype and grade on a cutaneous squamous cell carcinoma report](https://onco.cc/terms/cscc-subtype-and-grade/), [The WHO classification of breast tumours, and what the 6th edition changed](https://onco.cc/terms/who-breast-classification/), [TTF-1 and p40 (how lung histology is decided)](https://onco.cc/terms/ttf1-p40/)
- cancers: [Extrapulmonary neuroendocrine carcinoma](https://onco.cc/cancers/extrapulmonary-nec/), [Grade 3 well-differentiated neuroendocrine tumour](https://onco.cc/cancers/grade-3-net/), [Neuroendocrine tumours](https://onco.cc/cancers/neuroendocrine/), [Prostate cancer](https://onco.cc/cancers/prostate/), [Thyroid cancer](https://onco.cc/cancers/thyroid/)
- fronts: [Diagnostics & Biomarkers](https://onco.cc/fronts/diagnostics/)

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