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On 19th February
2002, at the TVCS meeting in Oxford, Behdad Shambayati, from
St Peter's Hospital, Middlesex, gave a topical presentation (in
view of the recent terminology discussions at the BSCC 2002), entitled
"How good are we at grading dyskaryosis".
Grading systems
to aid differentiation of degrees of dyskaryosis have been around
since Papanicolou in 1968.
By 1986 the
British Society for Clinical Cytology (BSCC) working party
put forward a grading system concentrating on nuclear/cytoplasmic
(N/C) ratio and thickness of involved epithelium. The system currently
in use in the UK has 3 grades of dyskaryosis - mild, moderate and
severe. A borderline category, also gives the woman an abnormal
report.
The Bethesda
System (TBS) however has only 2 grades.
LGSIL - low grade intraepithelial lesion correlating with mild dyskaryosis
HGSIL- high grade intraepithelial lesion correlating with moderate
to severe dyskaryosis
ASCUS (atypical squamous cells of uncertain significance) is a report
which tallies with our borderline category.
The criteria
for judging dyskaryosis are common to both systems. These are:
- cell size
and shape
- nuclear size
(at least 3 times normal)
- nuclear outline
(notches, indentation and protrusions)
- nuclear chromatin
increasingly coarse and granular and usually more hyperchromatic
- nuclear cytoplasmic
ratio -
mild dysk. - nuclear size increased, cytoplasm remains same
mod-severe dysk. - nuclear size increased, cytoplasm decreased
Internet website
available "Cervical Dysplasia Tutorial" by SUNY Health
Center at Syracuse (copyright 1998) with graphics.
The N/C ratio
is an all important but subtle judgement and is not easily reproducible.
Various methods of judging areas of the cell occupied by the nucleus
have been tried. Dr. Alan Rubin produced a paper describing diameter
measurements. Spriggs favoured a cytoplasmic approach. A search
on the Internet will reveal many publications on the subject by
Robert J Kurman and Diane Solomon .
Behdad raised the question: Do we need to measure areas at all?
Why not memorise examples of mild, moderate and severe dyskaryosis.
Screeners use N/C ratio, and adopt Spriggs's cytoplasmic approach
to grading mild, moderate and severe dyskaryosis (CIN I, II, and
III) without even realising it.
The ultimate
decision lies with the consultant and has vast implications regarding
treatment. As biopsies are taken at the time of treatment in most
cases of high grade lesions, accuracy of grading can be examined.
Behdad produced the statistical evidence available for 2001/2002
on the reporting of CIN II in England showing a ppv of 67-87% accuracy
with histological results.
We were urged
to consider the fact that in the UK we currently have in our system
too many grades, which often overlap. Fewer grades, as in the Bethesda
system would concentrate the mind and lead to good discipline when
grading.
The new thin-layer
liquid based cytology methods were briefly mentioned, and it was
suggested that although the ability to grade mild dyskaryosis was
comparable with conventional smears; the grading of moderate and
severe dyskaryosis was proving to be more difficult. The same criteria
for grading would still be needed but modified in view of improved
preservation of cells and isolation of individual cell types.
The lecture
concluded by urging us to take a pragmatic approach to the decisions
concerning the terminology to be adopted by BSCC in 2002, and be
open minded to new systems of grading.
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