The Bethesda System for Reporting Cervical Cytology

The Bethesda System: Historical Perspective

Terminology forms the basis for effective communication between the laboratory and clinician. The clinician is expected to provide relevant patient information to the laboratory. It is the laboratory's responsibility to report results using terminology that clearly conveys the diagnostic interpretation of the morphologic findings. The use of a uniform diagnostic terminology facilitates communication by establishing a common language that, in theory, does not vary significantly from cytologist to cytologist or laboratory to laboratory. However, terminology is not static over time; rather, it evolves in parallel with increased understanding of the pathogenesis and biology of disease. The framework, therefore, must be flexible enough to incorporate advances in scientific knowledge without creating undue confusion or complexity.

In 1988, the National Cancer Institute (NCI) sponsored an open workshop – including cytotechnologists, pathologists, clinicians, and representatives of professional organizations – to develop a uniform descriptive terminology for cervical/vaginal cytologic interpretation. The format that emerged became known as The Bethesda System (TBS).

Approximately 2 years later, a second meeting was convened to critique and refine the terminology based on experience with the use of the system in actual laboratory practice. Minor modifications were incorporated into the 1991 Bethesda System that streamlined the terminology. In addition, an ad hoc committee developed criteria for specimen adequacy and Bethesda interpretive categories, culminating in the first TBS atlas that outlined and illustrated the morphologic features. By the mid- to late 1990s, there was a significant penetration of TBS into cytopathology practice with approximately 90% of laboratories in the USA using the Bethesda terminology for reporting of cervical/vaginal cytology. Articles published since the release of the second manual have shown increased consistency of terminology across countries, which, has greatly facilitated communication between systems which until this time, had little hope of sharing gynecologic screening data.

The fundamental aim of TBS has been to communicate clinically relevant information from the laboratory to the patient's healthcare provider, using uniform, reasonably reproducible terminology, which reflects the most current understanding of the biology of cervical neoplasia. Advances in the understanding of the biology of cervical cancer, results from clinical trials, the introduction of liquid-based cytology, human papillomavirus (HPV) testing, and automated screening devices for cervical cytology led to the decision to convene the third Bethesda workshop in April 2001.

Report Format

The basic structure of TBS includes three elements, based on communication needs germane, but not limited, to gynecologic cytology: (1) statement of specimen adequacy, (2) general categorization, and (3) descriptive terminology. The specimen type – conventional smear, LBP, or other – should also be stated in the report ( Box 6-1 ).

Specimen Adequacy

Reporting of adequacy was an important quality assurance measure introduced by TBS. The 1988 Bethesda System incorporated a classification of three categories of specimen adequacy – satisfactory, less than optimal, and unsatisfactory – into the format of the report but did not outline specific morphologic criteria for evaluation of adequacy. Participants at the 1991 Second Workshop, and others in the cytopathology community, voiced the need for developing consensus guidelines. In response, following the second workshop, a Criteria Committee formulated the definitions for adequacy, based on a combination of experience and review of an admittedly sparse scientific database. Three categories – “satisfactory,” “satisfactory but limited by …,” and “unsatisfactory” – based on estimates of overall squamous cellularity, assessment of the transformation zone component, and the presence/extent of obscuring or limiting factors, were suggested in an initial attempt to develop a more standardized approach to the evaluation of adequacy. It was emphasized that the indicated percentages should be used as general ranges, not strict numerical cut-offs and that patient-related clinical factors and previous cytologic findings should always be taken into consideration.