From the Guidelines
The Bethesda System is a standardized reporting framework for classifying cervical cytology (Pap smear) results, categorizing findings into main groups including: Negative for Intraepithelial Lesion or Malignancy (NILM); Atypical Squamous Cells (ASC), which includes ASC-US (of undetermined significance) and ASC-H (cannot exclude HSIL); Low-grade Squamous Intraepithelial Lesion (LSIL); High-grade Squamous Intraepithelial Lesion (HSIL); and Squamous Cell Carcinoma. The system was developed in 1988 at the National Cancer Institute in Bethesda, Maryland, and has been updated several times since then, with the most recent update being the Bethesda System 2001 1. The Bethesda System also includes statements about specimen adequacy and other non-neoplastic findings, allowing for clear communication between laboratories and clinicians, and guiding appropriate patient management and follow-up based on the degree of abnormality detected 1. The classification is important because it correlates with the risk of developing cervical cancer and determines the appropriate intervals for screening and the need for additional testing such as HPV testing or colposcopy 1. Key categories in the Bethesda System include:
- Negative for Intraepithelial Lesion or Malignancy (NILM)
- Atypical Squamous Cells (ASC), which includes ASC-US (of undetermined significance) and ASC-H (cannot exclude HSIL)
- Low-grade Squamous Intraepithelial Lesion (LSIL)
- High-grade Squamous Intraepithelial Lesion (HSIL)
- Squamous Cell Carcinoma
- Atypical Glandular Cells (AGC)
- Adenocarcinoma in situ (AIS)
- Adenocarcinoma The system has been widely adopted and is recommended for use in clinical practice, as it provides a standardized and consistent approach to reporting cervical cytology results 1.
From the Research
Overview of the Bethesda System
- The Bethesda System is a classification system for reporting cervical/vaginal cytologic diagnoses, introduced to replace the numerical Papanicolaou class designations 2.
- The system was developed and approved at the National Cancer Institute workshop in Bethesda, MD, in 1988, and is a flexible guideline that can be modified as needed 3.
Classification Categories
- The Bethesda System includes the following categories for squamous epithelial lesions:
- Atypical squamous cells of undetermined significance
- Squamous intraepithelial lesion (SIL), which encompasses the spectrum of squamous cell carcinoma precursors, divided into:
- Low-grade SIL (human papillomavirus [HPV]-associated cellular changes, mild dysplasia, and cervical intraepithelial neoplasia [CIN] I)
- High-grade SIL (moderate dysplasia, severe dysplasia, and carcinoma in situ and CIN II and III)
- Squamous cell carcinoma 2.
Rationale and Significance
- The rationale for including HPV-related changes with CIN I within low-grade SIL is based on the morphologic, behavioral, and virologic similarity of these two lesions 2.
- The Bethesda System has been widely adopted and has contributed significantly to the understanding of cervical cancer, with its clinical relevance and clear implications for each category 4.
- The system has undergone revisions to incorporate technological and scientific advances, and its wide accessibility has made it an exemplary teaching-learning resource 4.
Historical Perspective and Evolution
- The Bethesda System was first introduced in 1988, with the aims of providing effective communication, facilitating cytologic-histologic correlation, and facilitating research into the epidemiology and biology of cervical disease 5.
- Over the past three decades, the system has evolved to become a multidisciplinary effort, with contributions from several stakeholders, and has been integrated with molecular methods for cervical cancer screening, triage, and prevention 5.