Leica PELORIS DUAL User Manual

High-Speed Processing of Large

TM

Specimens on the Peloris

Dual

Retort Tissue Processor

Geoffrey Rolls

Leica Microsystems, Biosystems Division, Melbourne, Australia

High-Speed Processing of Large Specimens on the
Peloris

TM

Dual Retort Tissue Processor

Geoffrey Rolls

Leica Microsystems, Biosystems Division, Melbourne, Australia

This paper presents the results of comparative evaluations carried out during field trials in two large
public hospitals, that set out to examine whether the design features of the Peloris dual retort tissue
processor led to reduced processing times for large specimens without compromising quality. In the
context of a busy histopathology laboratory, we demonstrate that the introduction of Peloris processing
would allow the processing of large, dense specimens in 6 hours leading to the completion of more runs
in a working day and the reduction of turnaround times.

Ten sequential six hour and nine hour processing runs were undertaken on a Peloris processor at either
45 °C or 55 °C and the resultant blocks and sections were evaluated for quality using a comprehensive
scoring system. Peloris results were compared to those achieved on a matched panel of specimens
processed using a processor that represents the industry standard (the Tissue-Tek
show that for large, dense specimens Peloris can produce results of an equivalent standard to an
“overnight” schedule (13 hours) run on a VIP using much shorter schedules. Results also indicate that
there is some advantage in processing at higher temperature (55 °C) for both the six and nine hour
schedules.

®

VIP™). The results

Introduction

A fundamental requirement in the histopathology laboratory is to
safely and effectively process specimens. Sectioning of paraffin
blocks should be straightforward with the resultant sections
being of a high standard demonstrating excellent morphological
detail. This applies to the complete range of specimen types and
sizes, ranging from tiny, delicate fragments to sizeable wedges
of dense tissue. In busy laboratories these requirements must be
balanced against increasing demands to reduce turnaround times,
to process greater numbers of specimens and to complete more
runs in the working day.

The traditional view embraces a conservative approach to
processing of all specimen types. A survey of standard histology
texts published in the last twenty years reveals an average
processing time of 15.7 hours for “routine overnight processing”
using xylene as a clearing agent. A survey of local and international
laboratories shows that the average duration of a “routine
overnight” schedule on an enclosed processor using xylene and
excluding any additional fixation steps is 10.3 hours (see Table 1 for
details). Of course these laboratories do use shorter schedules for
special purposes, where particular types of specimens are to be

processed (eg. endoscopic biopsies), or where specimens falling
within strict size limits are included.

These field trials were conducted by Vision BioSystems (VBS).
Vision Biosystems has since formed part of the Biosystems Division
of Leica Microsystems. What is needed then, is a processor which
can effectively process a full load of cassettes, say 200 – 300 per
retort, containing the complete range of tissues normally included
in a “routine overnight run”, but doing so in a much shorter time,
preferably within the six hour threshold that would allow them
to be completed within one working day. The Peloris dual retort
tissue processor has been designed with these requirements in
mind. Compared to processors representing the current industry
standard it has a much faster and more even heating response in
the retorts, fast fill and drain actions, a basket design allowing better
fluid exchange with reduced reagent carryover, and more effective
agitation. These features are designed to reduce processing times.
The purpose of this paper is to present the results of comparative
evaluations carried out during field trials that set out to show that
the design features of Peloris lead to reduced processing times
without compromising quality.

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Number of Labs Types of Processor

(number)

25 Leica TP1050 (20)

VIP (4)
Shandon (1)

Table 1. Routine overnight processing schedules

Schedule Description Average Number

of Steps

Routine overnight 13 12 620 694

Average Number
of Steps Excluding
Fixation

Average Total Time
Excluding Fixation
(minutes)

Average Total Time
(minutes)

Independent field trials were carried out in two large public
teaching hospitals in Melbourne, Australia, during 2003 and 2004.
They were conducted in the Anatomical Pathology laboratories
of the Royal Melbourne Hospital (RMH) (1200 beds) and at Austin
Health (AH) (840 beds). The evaluations relating to processing speed
were conducted in a similar fashion during both field trials. They
involved senior histology scientists from both external laboratories
together with scientists from Vision BioSystems, in the assessment
of processed blocks and stained sections from a number of
processing runs. Using duplicate sets of matched specimens of
a variety of dimensions and types, multiple processing runs were
carried out using Peloris and an “industry standard” processor
in each laboratory (in both cases a Tissue-Tek VIP). Results from
Peloris rapid schedules run at 45 °C and 55 °C were compared with
VIP standard “routine overnight schedules” currently used in each
laboratory which served as a normal control.

Processing at elevated temperatures is widely accepted as a
means of accelerating processing by increasing diffusion rates
in specimens (1, 2) although some authors believe that this can
cause additional shrinkage and staining problems (2, 3). We have
certainly not found this to be the case during extensive testing of
Peloris. These trials provided an opportunity to compare results of
rapid processing at 45 °C and 55 °C and to confirm that there were
no adverse effects from using the higher temperatures.

The assessments were carried out independently with staff at
the external sites using slightly different scoring methods, with
the assessors being unaware of the schedules used to process
the specimens. The scoring system used by VBS staff has been
extensively used throughout the development and testing of Peloris
to evaluate the quality of tissue processing and as a mechanism for
optimizing standard processing protocols. A score is calculated by
assessing 23 parameters and is expressed as a percentage. The
complete details are provided elsewhere(4).

Method

Testing throughout the RMH and AH trials was conducted such
that all processing results were compared directly to those of their
existing tissue processors (RMH - Tissue-Tek VIP 4, AH Tissue-Tek
VIP 5). As far as possible specimens for assessment were kept
identical in terms of size, fixation and source on both instruments
for each processing run. All specimens were thoroughly fixed. Not
every specimen in each run was evaluated. Any specimens that
were not for evaluation but loaded into retorts on Peloris to provide
a representative case load comparable to the VIP, consisted of pig
tissue supplied by VBS. Typical specimens used in assessment of
processing and their approximate dimensions are shown in Table 2.

At each laboratory for each of 10 sequential working days, three
processing runs were carried out. Two rapid schedules were run
on Peloris using the two retorts. Retort A was used for the 6 hour
schedule and Retort B for the 9 hour. Runs were carried out daily
at either 45 °C or 55 °C. For each 6 and 9 hour run on Peloris a
routine overnight run was completed on a VIP containing a normal
diagnostic specimen load together with a set of the duplicate test
specimens (200 – 250 cassettes). These served as our normal
control group. Fresh reagents were provided for run 1 and not
changed for the 10 runs on both Peloris and the respective VIP.
For each Peloris run, in addition to the test specimens, cassettes
containing various pig tissues were included to take the specimen
number to 228, which provided an equivalent specimen load to that
in the respective VIP processor (75% capacity of each retort). The
processing schedules used are shown in Tables 3 and 4. Figure
1 illustrates the difference in step times between the various
schedules used. Note that the total pump and drip times in the
Peloris schedules are considerably shorter than those of the VIP.

Royal Melbourne Hospital (RMH) Austin Hospital (AH)

Tissue Dimensions (mm) Tissue Dimensions (mm)

Intestine 15 x 10 x 5 Intestine 30 x 8 x 5

Liver (pig) 25 x 15 x 5 Intestine 20 x 15 x 5

Spleen 15 x 10 x 5 Liver (pig) 20 x 20 x 5

Lung 25 x 15 x 5 Liver 30 x 25 x 5

Kidney (pig) 15 x 10 x 5 Lung 20 x 20 x 5

Heart (pig) 20 x 15 x 5 Lung 20 x 15 x 5

Thyroid 20 x 10 x 5 Kidney (pig) 20 x 15 x 5

Skin 30 x 25 x 5 Kidney 15 x 15 x 5

Breast 30 x 25 x 5 Heart (pig) 20 x 20 x 5

Prostate Chips Heart 20 x 15 x 5

Table 2. Typical specimens used in assessment of processing

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