# International System for Reporting Serous Fluid Cytopathology

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

## TL;DR

This system is how the result of testing fluid drained from around the lungs, heart or abdomen is reported, in six categories from non-diagnostic to cancer that started there or spread there.

## Summary

The International System for Reporting Serous Fluid Cytopathology (Crothers and colleagues, 2020) has six diagnostic categories adapted from earlier cytopathology systems: non-diagnostic, negative for malignancy, atypia of undetermined significance, suspicious for malignancy, malignant primary (a cancer arising in the lining, such as mesothelioma) and malignant secondary (a cancer that has spread there). Each carries a risk of malignancy supported by meta-analysis.

## Fields

- Kind: Term
- Last checked: 2026-11-04
- Also known as: International System for Reporting Serous Fluid Cytopathology; TIS serous fluid

## Sources

- Crothers et al., The International System for Reporting Serous Fluid Cytopathology: introduction and overview of diagnostic terminology and reporting (Springer 2020): https://doi.org/10.1007/978-3-030-53908-5_1

## Connected records

- terms: [Bethesda category (thyroid cytology)](https://onco.cc/terms/bethesda-category/), [Malignant pleural effusion](https://onco.cc/terms/malignant-pleural-effusion/), [Malignant pleural effusion and ascites](https://onco.cc/terms/pleural-effusion/), [WHO Reporting Systems for cytopathology](https://onco.cc/terms/who-cytopathology-reporting-systems/)
- cancers: [Mesothelioma](https://onco.cc/cancers/mesothelioma/)

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