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On 27th May
2002 at the TVCS meeting at Northwick Park Hospital Dr Mary Falzon
reported that benign conditions that mimic malignancy are common
in cytology. She quoted 'Cytology is not a test result but a medical
opinion and is dependent on interpretation'.
In cytology,
an 'over-call' is recorded as a false positive, and an 'under-call'
- missing or undercalling an abnormal smear - is recorded as a false
negative.
Dr Falzon identified
potential false positives such as
- immature
squamous metaplasia,
- regenerative
changes,
- inappropriate
and metaplastic glandular cells and
- reactive
changes in endocervical cells.
Squamous
lesions versus squamous metaplasia
Squamous
metaplasia
- nuclear enlargement
- N/C ratio
slightly
- increased
smooth nuclear membrane
- nucleoli
have a regular outline
- there may
be an Increase in density of the cytoplasm which has distinct
cell borders
- a central
nuclear groove.
Regenerative
changes
- changes mimicking
dyskaryosis may be found in smears with previous radiotherapy.
- regenerative
changes are also found in vault smears and in smears of women
undergoing Cytotoxic therapy.
- follicular
cervicitis may occasionally be misinterpreted as severe small
cell dyskaryosis CIN 3. Follicular cervicitis with its numerous
lymphocytes can also mimic a lymphoma.
Atrophic
smears are a potential source of false positives. Atrophic smears
are found in Postmenopausal women and Post natal women. Contraceptive
pills and other
Forms of Androgenetic hormone also produce atrophy.
Endocervical
lesions are a major source of false positives.
- Cervical
polyps - may resemble glandular intraepithelial neoplasia,
ulceration and inflammatory changes
- Decidual
changes/ stromal cells, - microglandular hyperplasia and tuboendometrioid
metaplasia were all described and slides of difficult cases were
used to hi light the problems.
- Tuboendometrioid
metaplasia - is seen after surgery on the cervix. Regenerative
changes occur in 30 to 60 % of patients post operation and may
co exist with endometriosis.
- Tubal
metaplasia
- rounded granular nuclei; cilia; compact cohesive groups; no
feathering
- Endometrial
- blood stained; macrophages;crowded cell groups; uneven nuclear
membrane
- IUCD -
changes may be seen in 100% of endocervical cells and 40% of squamous
cells. These are associated with enlarged hypercromatic endocevial
cells; inflamation; 'bubblegum' cells; papillary fragments; high
N/C ratio. Outline of the nucleus is smooth and chromatin is finally
distributed.
- Hystiocytes
- may mimic severe dyskaryosis although the N/C ratio remains
the same in hystiocytes.
Awareness of
all these potential false positives or pseudomalignacies and the
step by step criteria and excellent slide collection for each of
the above mentioned conditions demonstrated by Dr Falzon in her
lecture will improve the interpretation of these potential false
positives.
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