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An assessment of the artefacts introduced by mounting two parallel sections from each histological level of cervical punch biopsies.
  1. Mark K Heatley1
  1. 1Department of Pathology, The Royal Liverpool University Hospitals, Broadgreen and Liverpool, Fifth Floor, Duncan Building, Prescot Street, Liverpool L7 8XP, UK

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    A previous study1 that compared different methods of orienting cervical biopsies has been extended to determine the optimal method of mounting the sections, cut from these biopsies, on the slide to ensure that they are clearly visible for histological examination under the coverslip.

    In this department six levels have traditionally been cut from each cervical biopsy, with two adjacent sections from each level being mounted on either side of the midline along the long axis of the slide. This practice places the sections in close proximity to the edge of the coverslip where they may not be protected if the coverslip moves medially or where they may become obscured if mountant is squeezed from between the slide and the coverslip, and becomes smeared over the edge of coverslip.

    Two hundred routine cervical punch biopsies in which duplicate sections from each level were mounted on either side of the midline were assessed prospectively up to July 1999. They were compared with 47 biopsies, mainly gastric, duodenal, and rectal, in which a single section from each level was mounted at the midline of the slide. The slides were reviewed by a single pathologist who assessed the following features.

    1. Is part of one or more of the the sections from each level incompletely covered by the coverslip leaving it at least partially unprotected?

    2. Is part of one or more of the the sections from each level completely or incompletely covered by the mountant? As a result of being covered by mountant, are

    3. one or more of the sections from each level partially or completely obscured? This category was included to distinguish those cases in which, despite mountant having been smeared over the coverslip, it had retained its transparency, permitting the features in the underlying section to be assessed from those cases in which the mountant was no longer transparent and obscured the section.

    4. In each case the number of levels at which both sections from any particular level were obscured or uncovered was also assessed, because it could be argued that the above only presents difficulties if both sections from each level are obscured or uncovered, as each section has a duplicate cut at only 4 μm from it, which can also be assessed.

    Cases were only included in the “obscured” categories if the tissue was covered. Slides in which mountant was present on a part of the coverslip which did not sit over tissue were considered adequate for diagnostic purposes and not included, although it is recognised that they may not meet technical standards of perfection.

    Statistical analyses were performed using the Mann Whitney U test. A p value of less than 0.05 was considered to be significant.

    The results are presented in table 1. In 16% of cases in which duplicate sections had been mounted from each level, one or more section was not protected by the coverslip as opposed to 2% of cases where a single section was mounted at each level. At least one section was covered (62.5%) or obscured (53.5%) by mountant when duplicate sections were mounted from each level; the corresponding percentages when a single section was mounted at each level were 16.3% and 4.7%. Where duplicate sections from a given level had been mounted, both sections were at least partly obscured by the mountant representing a potentially serious limitation in the diagnosis of such cases in 21% of cases.

    Biomedical scientists should be discouraged from mounting parallel sections from histological levels because of the difficulty in ensuring that a section of adequate technical quality will be produced.

    Table 1

    The number of sections not covered by the coverslip that were covered by balsam, and the number of levels where material was obscured by balsam; if two levels were mounted the level was only considered to be obscured if both sections were obscured

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