Cytology and AMBS 2004 terminology for reporting

Background

In 1991, the US National Cancer Institute (NCI) sponsored a multidisciplinary meeting in Bethesda, Maryland to consider Pap smear terminology. Participants including pathologists, cytotechnologists, gynaecologists and primary care health professionals (predominantly from the USA, but also from other countries) agreed on a consistent system for reporting Pap smears: The Bethesda System 1991 (TBS 1991).[1]

NHMRC Australian terminology, 1994

As part of preparing the first National Health and Medical Research Council (NHMRC) 1994 guidelines for the management of women with screen-detected abnormalities,[2] the Australian working party considered the Bethesda terminology and recommended a range of modifications that resulted in a unique Australian terminology system.

Revisions of The Bethesda System 2001 (TBS 2001) and 2014 (TBS 2014)

There have been few changes in terminology since 2001.[3][4] In 2014, a smaller working party of cytopathologists, clinicians and epidemiologists reviewed TBS 2001, resulting in the 2014 update of The Bethesda System (TBS 2014) published in 2015.[5] Changes included additional information on cytology at other anatomical sites, adjunctive HPV testing, immunochemical assays such as dual p16 and Ki67 staining, and computer-assisted interpretation of cytology.

Australian Modified Bethesda System (AMBS 2004): current terminology in Australia

Building on the historical NHMRC Australian terminology from 1994, the Australian Modified Bethesda System (AMBS) was introduced in 2004. AMBS 2004:

• incorporated the separation of suspected from confidently predicted low-grade abnormalities
• reflected a modern understanding of the relationship between HPV infection and cervical cancer and its precursors
• was compatible with terminology systems used internationally
• did not mandate distinctions for which there is poor evidence for reproducibility or clinical significance.

There has been no change to the AMBS since 2004 and it remains the current terminology in Australia. Table 3.1 compares AMBS 2004 with TBS 2001 and TBS 2014.

Table 3.1. Comparison of the Australian Modified Bethesda System (AMBS 2004) and The Bethesda System (TBS 2001/2014)

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Squamous abnormalities

Possible low-grade squamous intraepithelial lesion

The category of possible low-grade squamous intraepithelial lesion (pLSIL) is to be used when the reporting scientist/pathologist observes changes in squamous cells that may represent a low-grade squamous intraepithelial lesion, but the changes are not so clear-cut as to justify a ‘definite’ diagnosis. This category specifically excludes changes that are within the scope of reactive processes..

Low-grade squamous intraepithelial lesion

The low-grade squamous intraepithelial lesion (LSIL) category is the morphological correlate of productive viral infection. It is to be used when the scientist/pathologist observes changes that, pre-AMBS 2004, would have been described as ‘HPV effect’ or ‘CIN1’. 

Possible high-grade squamous intraepithelial lesion

The category of ‘possible high-grade squamous intraepithelial lesion’ (pHSIL) is to be used when the reporting scientist/pathologist suspects the presence of a high-grade squamous abnormality, such as CIN2, CIN3 (in the pre-AMBS 2004 system) or squamous cell carcinoma (SCC), but the changes are insufficient to justify a confident cytological prediction of a high-grade lesion.

High-grade squamous intraepithelial lesion

The high-grade squamous intraepithelial lesion (HSIL) category is the morphological correlate of a true preneoplastic change occurring in squamous cells as a result of HPV infection. It is to be used when the scientist/pathologist observes changes that, pre-AMBS 2004, would have been described as CIN2 or CIN3. 

If, in addition to the presence of a definite intraepithelial high-grade abnormality, there are features that suggest the presence of an invasive component, this should be noted in the ‘specific diagnosis’ section of the report.

Squamous cell carcinoma

The SCC category is self-explanatory.

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Glandular abnormalities

Atypical endocervical cells of undetermined significance
Atypical glandular cells of undetermined significance

These categories encompass those changes in glandular cells that the reporting scientist/pathologist believes are outside the scope of a definite reactive process. 

It has been well documented that productive HPV infection does not exist in glandular cells, and therefore there is no glandular correlate to the low-grade squamous abnormality. Nevertheless, the morphological changes observed in glandular cells encompass a spectrum of changes. 

These categories should be used when such changes are insufficient to raise the possibility of a neoplasm, such as AIS, but are beyond those accepted as definitely representing a reactive process. 

Cells in this category are to be designated as follows:

• atypical glandular cells when the reporting scientist/pathologist is not sure whether the cells are endocervical
• atypical endocervical cells when the reporting scientist/pathologist is confident that the cells are endocervical

Possible high-grade glandular lesion

This category is to be used when the reporting scientist/pathologist suspects the presence of a high-grade glandular abnormality such as possible AIS, possible endocervical adenocarcinoma or possible endometrial adenocarcinoma, but is unable to make a confident prediction.

Endocervical adenocarcinoma in situ

The endocervical AIS category is self-explanatory. The diagnosis is to be used when the reporting scientist/pathologist is confident of the presence of AIS.

Adenocarcinoma

The adenocarcinoma category is self-explanatory. The reporting scientist/pathologist has the option of designating whether they believe the adenocarcinoma is endocervical, endometrial or extrauterine in origin.

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