# Yokohama System for Reporting Breast Fine-Needle Aspiration Cytopathology

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

## TL;DR

The Yokohama System puts the result of a needle test on a breast lump into one of five categories: insufficient, benign, atypical, suspicious for cancer, or cancer.

## Summary

The International Academy of Cytology published the Yokohama System for breast fine-needle aspiration biopsy cytopathology in 2019 (Field and colleagues, Acta Cytologica). Validation studies describe its five categories: 1 insufficient material, 2 benign, 3 atypical, 4 suspicious for malignancy and 5 malignant, each with a risk of malignancy. In one 63-case series with surgical follow-up the risk was about 2% for benign, 33% for atypical and 100% for suspicious and malignant (Gowri and colleagues, Cureus 2026); small series vary.

## Fields

- Kind: Term
- Last checked: 2026-11-04
- Also known as: Yokohama System; IAC Yokohama System

## Sources

- Field et al., The International Academy of Cytology Yokohama System for Reporting Breast Fine Needle Aspiration Biopsy Cytopathology (Acta Cytol 2019): https://doi.org/10.1159/000501055
- Gowri et al., Validation of the International Academy of Cytology Yokohama System for reporting breast fine-needle aspiration cytopathology (Cureus 2026): https://doi.org/10.7759/cureus.113225

## Connected records

- terms: [Bethesda category (thyroid cytology)](https://onco.cc/terms/bethesda-category/), [BI-RADS (Breast Imaging Reporting and Data System)](https://onco.cc/terms/bi-rads/), [Core needle biopsy and fine-needle aspiration (FNA)](https://onco.cc/terms/core-needle-biopsy/), [WHO Reporting Systems for cytopathology](https://onco.cc/terms/who-cytopathology-reporting-systems/)
- cancers: [Breast cancer (all types)](https://onco.cc/cancers/breast-cancer/)

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