Bethesda System

Author: Andreia Carreira. See authors page.
Last edited: Pathologika, April 29, 2017
Cite this page: Carreira, A., Bethesda System. Available at: [Accessed: date].
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Bethesda system, why?

The Bethesda System for reporting cervico-vaginal cytology reports dates back to December 1988. This was the first time a group of individuals with experience in cytopathology, histopathology, and medical practice had met at the National Institutes of Health in Bethesda, Maryland.

This meeting, which became Bethesda’s first workshop, aimed to establish the terminology that would give clear indications for patient management as well as to reduce inter-observer variability. During the 2 days of the meeting, 3 fundamental principles were created that have been guiding Bethesda’s terminology and which continue to this day:

  1. Terminology should communicate clinically relevant laboratory information to the patient’s healthcare provider;
  2. Terminology must be uniform and reasonably reproducible between different pathologists, technicians and laboratories and also flexible enough to be adapted to a wide variety of laboratory configurations and geographic locations;
  3. Terminology should reflect the most current understanding of cervical cancer.

The meeting provided the Bethesda Terminology, which represents a diagnostic system, with clinically relevant, uniform and reproducible information among different pathologists, as well as with relevant meaning for the clinician, in order to reflect a better understanding of the neoplasia.

It is the most used nomenclature to classify the anomalies of the squamous as well as the glandular epithelium.

Epithelial squamous cell anomalies can be categorized as:

  • cell anomalies of undetermined significance (ASC-US),
  • low grade intraepithelial lesion (LSIL),
  • high grade intraepithelial lesion (HSIL),
  • invasive carcinoma.

Epithelial glandular anomalies can be categorized as:

  • atypical glandular cells of undetermined significance (AGC),
  • in-situ endocervical adenocarcinoma (AIS),
  • endocervical adenocarcinoma,
  • endometrial adenocarcinoma,
  • adenocarcinoma NOS.

Over time, this Bethesda nomenclature has undergone changes in order to reduce confusions between benign and atypical cell changes.

The most significant change occurred with the elimination of the category of moderate dysplasia (CIN II).

Low-grade intraepithelial lesion (LSIL – suggestive of HPV infection) replaced grade I intraepithelial neoplasia (CIN I).

High-grade intraepithelial lesion (HSIL) replaced the categories of CIN II and III.

The classification of ASC-US (atypical squamous cells of undetermined significance) was reviewed in 2001 and reclassified in ASC-US (atypical squamous cells of undetermined significance) and ASC-H (atypical squamous cells without excluding lesion (high-grade intraepithelial) to distinguish cases in which there is a greater probability of precursor lesion. In these cases, the patient should be referred for colposcopy.

The decrease of diagnostic categories provided a better diagnosis as well as reproducibility among different observers.

Following the first introduction of terminology in 1988, revisions have already taken place in 1991, 2001 and recently in 2014.


Solomon D: Foreword; in Nayar R, Wilbur DC (eds): The Bethesda System for Reporting Cervical Cytology: Definitions, Criteria, and Explanatory Notes, ed 3. New York, Springer 2015.