# Lesion

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

## TL;DR

A doctor's neutral word for any abnormal patch of tissue seen on a scan or examination: a lump, a nodule, a shadow. It may or may not be cancer until a biopsy says so.

## Summary

Radiologists describe lesions by size, shape, edges and behaviour on contrast; suspicious features prompt biopsy, and in trials the measurable 'target lesions' are what RECIST tracks to decide whether a drug is working. A lesion is 'measurable' if it is large enough to be measured reliably (10 mm for most tumours, 15 mm for lymph nodes on their short axis). Precancerous lesions (colon polyps, cervical dysplasia, Barrett's oesophagus) are abnormal tissue that has not yet become invasive cancer and are the target of screening programmes.

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: lesions; target lesion; target lesions; nodule; nodules; spot on the scan

## Sources

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

## Connected records

- terms: [Biopsy](https://onco.cc/terms/biopsy/), [In situ](https://onco.cc/terms/in-situ/), [Primary tumour](https://onco.cc/terms/primary-tumour/), [RECIST](https://onco.cc/terms/recist/), [Screening](https://onco.cc/terms/screening/)
- technologies: [CT (computed tomography)](https://onco.cc/technologies/ct/), [MRI](https://onco.cc/technologies/mri/), [PET/CT](https://onco.cc/technologies/pet-ct/)

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JSON: https://onco.cc/api/v1/entities/lesion.json