6
The Bethesda System for Reporting cervical cytology
Sampling of the Transformation zone
Presence of endocervical or squamous metaplastic cells forms the
microscopic basis for the assumption that the transformation zone
has been sampled. The numeric criterion for a transformation zone
component, at least 10 well preserved endocervical or squamous
metaplastic cells, did not change from TBS 1991; however, due
to the widespread utilization of liquid-based preparations, single
endocervical/metaplastic cells are acceptable and clusters are no
longer required. This definition applies to specimens from both
premenopausal and postmenopausal women having a cervix. In
the situation of marked atrophy, where metaplastic and endocer-
vical cells often cannot be distinguished from parabasal cells, the
laboratory has the option of making a comment regarding the diffi-
culty in assessing the transformation zone component. Patient fac-
tors, such as location of the transformation zone, age, pregnancy,
and previous therapy, may limit the clinician's ability to obtain an
endocervical sample despite optimal collection technique.
Numerous cross-sectional studies have demonstrated that
smears with endocervical and/or metaplastic cells have a signifi-
cantly higher frequency and higher grade of squamous epithe-
lial abnormality detected than do smears without such cells.19-22
Paradoxically, short-term longitudinal studies of women whose
initial negative smears lacked an endocervical component have
shown no increase in abnormalities on repeat, satisfactory
smears (as might be expected if the initial smears had a higher
false-negative rate).23,24
Based on the above studies, TBS 2001 does not require the
presence of a transformation zone component to categorize a
specimen as satisfactory—adequate squamous cellularity is the
only criterion. The absence of a transformation zone compo-
nent is considered to be a quality indicator. With the reported
increase in endocervical carcinoma,25,26 the importance of the
transformation zone component may undergo further evalu-
ation in the future, in order to ensure optimized screening
performance in the setting of endocervical neoplasia.
Management Guidelines
The ASCCP has published management guidelines for Pap test
specimen adequacy and quality indicators.9 The preferred man-
agement for unsatisfactory Pap tests is a repeat test within a short
interval of 2-4 months. Unsatisfactory cases are unreliable for
detection of an epithelial abnormality; furthermore a longitu-
dinal study found that unsatisfactory Pap tests are more often
from high-risk patients and have significantly more SIL/cancer
on follow-up than patients with satisfactory index Paps.27 The
guidelines suggest a repeat Pap test in 12 months for most women
who lack a transformation zone component or whose cytology
is partially obscured unless there is a history of prior adequate/
negative Pap tests. Indications for considering earlier repeats are
also outlined and depend on additional patient risk factors.28
For quality assurance, it may be prudent to have the patholo-
gist review unsatisfactory cases prior to final sign-out because of
the clinical implications of such a report and the association of
obscuring blood/inflammation with invasive cancers.29
impact on Laboratory Practice
The incorporation of specimen adequacy as an integral part
of the cervical cytology report has been acknowledged as one
of the most important contributions of TBS. The impact on
laboratory practice has been dramatic. Surveys conducted by
CAP revealed that in 1990 only 35% of responding labora-
tories routinely reported specimen adequacy; by 1992, this
figure increased to 85%.30 A 1991 CAP survey found that
most laboratories reported unsatisfactory specimen rates of
0.5-1.0% . By the year 2003, a CAP survey assessing Bethesda
implementation and reporting rates31 found that 73.6% of
responding laboratories had eliminated the use of the "sat-
isfactory but limited by.
.." category and the 2001 TBS mini-
mum squamous cellularity criteria had been adopted by
85.3%. Experts had predicted an increase in unsatisfactory
rates with the use of TBS 2001 criteria. While some studies
have indeed reported this (up to a tenfold increase on con-
ventional smears32), the CAP survey31 and other reports from
the United States33 and Europe34 did not show an increase
in the unsatisfactory rate after conversion to TBS 2001 ade-
quacy criteria. Possibilities suggested by the authors include
improved sampling and preparation methods, related pre-
dominantly to liquid-based methodology, or, alternatively,
lack of attention to the TBS 2001 criteria.31
General Categorization
The general categorization is a clerical device to aid clinicians and
their office staff in triaging patients/prioritizing cases for review
and to assist laboratories in compiling statistical information.
There are 3 headings used under the general category:
1. "Negative for intraepithelial lesion or malignancy"
for specimens in which an epithelial abnormality is
not identified. Organisms and other benign/reactive
cellular changes can be reported in the Interpretation
under this category.
2. "Other" may be utilized for cases in which there is
no clear cytologic abnormality but the findings may
warrant follow-up/investigation based on patient risk,
for example endometrial cells in a woman 40 years of
age or older.
3. "Epithelial cell abnormality" may be utilized for squa-
mous or glandular epithelial abnormalities. Specify as
far as possible which type is present.
If more than one diagnostic entity is present—for exam-
ple, an infectious process and an epithelial abnormality—the
specimen should be categorized according to the most clini-
cally significant lesion; in this example, epithelial cell abnor-
mality. However, the general category should not replace
narrative (descriptive) terminology for communicating the
interpretation/result. Some laboratories also extend the con-
cept of a general or summary categorization to nongynecologic
specimens.
Interpretation/Result
The prior Bethesda system use of the term "diagnosis" was
replaced by "interpretation/result" in 2001. Workshop partici-
pants felt that cervical cytology is a screening, not a diagnostic
test, that provides the clinician with information on morpho-
logic findings that need to be integrated with the patient's
other clinical findings for a final diagnosis and subsequent
management.7
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