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].

The Bethesda system was created in 1988 with the aim of being a representative 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.