Specimen orientation:
Correct orientation
of the specimen is crucial and in the case of Whipple’s specimens this
is aided by identification of the gastric, duodenal, pancreatic and bile
duct surgical margins.
It is useful to
remember that the common bile duct enters the superior border of the
pancreas just below the distal greater gastric curvature and close to
the posterior plane of the specimen. A portion of superior mesenteric
vein wall may be adherent to the anterior aspect of the specimen.
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Initial
specimen preparation:
- The type of
specimen should be recorded.
-
Where applicable,
the length of the gastric and duodenal components, the pancreas and the
extrapancreatic common bile duct should be recorded.
-
The presence and
size of any omental or mesenteric tissue should be noted.
-
The stomach (if
present) and duodenum should be opened and cleaned, making sure that the
latter is incised along the border opposite to the pancreas. The
pancreas may also be incised at this stage .
- The specimen can
then be pinned to a cork mat and left for further formalin fixation for
at least 24 hours.
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Marking
of resection margins:
- The anterior
peritoneal surface of the pancreas, retroperitoneal surgical margin
and superior mesenteric vein surgical margin should be marked with
different colors of ink.
- Careful drying of
the specimen is essential before applying the ink, to minimize color
mixing and potential future confusion over margins.
- Specimens marking
may be performed before or after further formalin fixation, but inking
of all margins is strongly recommended prior to incision of the
pancreas.
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Specimen
dissection:
The pancreatic
surgical margin will often have been taken already as a frozen section
but may alternatively be sampled at this stage.
Opinion is varied
regarding the optimum method of incising the pancreas but the key is to
be able clearly to demonstrate:
(1)
the lesion and ; (2) the surgical margins.
- The
most commonly used method involves making a series of parallel incisions
through the pancreas in the horizontal plane, usually extending the
incision through the adjacent duodenum.
- One of the
incisions may be made through the ampulla of Vater if a lesion is
present in this area.
-
However, lesions
sited primarily within the lower common bile duct may be best
demonstrated via one or more incisions in the coronal plane.
-
Whichever technique
is used, it is often useful to pass a metal probe through the ampulla of
Vater or common bile duct as a guide when choosing the position of
first incision, particularly when visualization of one or both of these
structures are required.
- The incision may
alternatively be made prior to further formalin fixation, but care must
be taken not to disrupt the surgical margins.
- The maximum
diameter of any lesion should now be recorded as well as an estimation
of its distance from the main surgical margins.
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Block
selection:
- The number of
blocks taken will vary with the nature of the lesion.
- However, a general
guide would be to take at least three blocks of any lesion to include
the inked surgical margins, together with the common bile duct margin
and pancreatic surgical margin if not separately sampled.
- If segmental
excision of the superior mesenteric vein has been performed, its margin
should also be sampled.
- Large, cystic and
multicentric lesions will require more extensive sampling and a rate of
one block per 1-2 cm of lesion diameter is recommended.
- Most pancreatic
lesions, apart from some cystadenomas and intraduct proliferations, will
be unicentric in nature.
- Representative
sections should be taken from the distant pancreas, stomach, duodenum
and gallbladder to exclude background abnormality.
- Usually the section
that is macroscopically most representative is taken as a large block.
- This is not
essential but, especially if taken in the horizontal plane, facilitate
correlation of the histopathological and CT scan appearances.
- The major regional
lymph node groups will require dissection from the main specimen unless
received separately.
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