Anatomic Pathology / FIXATION ARTIFACT
Disparate Surgical Margin Lengths of Colorectal Resection
Specimens Between In Vivo and In Vitro Measurements
The Effects of Surgical Resection and Formalin Fixation
on Organ Shrinkage
Neal S. Goldstein,
MD,1 Anjana
Soman,
MD,1 andjordy
Sacksner,
MD2
Key Words: Colon; Rectum; Adenocarcinoma; Margins of resection; Surgery
Abstract
We noticed almost routine disparate results in
margin lengths when colorectal specimens are
measured in vivo by the surgeon and in vitro by the
pathologist. We studied 26 sigmoid and rectum
specimens to document the amount of organ shrinkage
after surgical removal and fixation. Each specimen had
a 5.0-cm segment at each end of the specimen marked
by serosal sutures before vascular devitalization. The
segments were measured after the specimen sat unfixed
for 10 to 20 minutes and after 12 to 18 hours of
formalin fixation. The segments shrank to a median
length of 3.0 cm (40% of the in vivo length) after 10 to
20 minutes and an additional 0.85 cm, to a median
length of 2.15 cm, after fixation. Overall after fixation,
the segments shrank 57% of the in vivo length.
Approximately 70% of the shrinkage occurred during
the first 10 to 20 minutes after removal, and the
remaining 30% occurred after fixation. For optimal
accuracy, margin distance must be obtained
immediately after surgical removal. Once the specimen
has been removed for several minutes, the difference
between unfixed and fixed margin lengths is 30%. A
correction factor of approximately 2x should be applied
when interpreting the margin length.
© American Society of Clinical Pathologists
The distance between an adenocarcinoma and edge of a
colonic resection specimen is one of the vital components in
the assessment of excision adequacy. Surgeons strive to
achieve a 5-cm length of bowel in the sigmoid and a 1-cm
length in the rectum between the neoplasm and distal end of
the specimen because shorter lengths are associated with
local recurrence. 1-3 We noticed almost routine disparate
results in margin lengths when the specimen is measured in
vivo by the surgeon and in vitro by the pathologist. Pathology
and surgical lore attributes this difference to organ shrinkage
during fixation. However, we have noticed that differences in
margin length also occur in unfixed specimens. We studied
sigmoid and rectum resection specimens to document the
amount of organ shrinkage that occurs after surgical removal
and fixation. These values can be used as correction factors
when interpreting surgical margin lengths when margins are
measured by the pathologist in fresh and fixed specimens.
Materials and Methods
We studied 26 sigmoid and rectal resection specimens
that were resected by one of us (J.S.). Of these, 18 specimens
were resected for the treatment of adenocarcinoma, and the
other 8 were resected for the treatment of diverticulitis. Two
patients had adenocarcinoma and diverticulosis.
All of the specimens were processed in an identical
manner. 4 Before vascular devitalization and surgical
removal, 2 serosal sutures were placed close to the lines of
resection of each specimen. A ruler was used to measure 5.0
cm back from each of the sutures, and 2 additional serosal
sutures were placed to mark these distances. The 5.0-cm
distance was measured while the specimen was straightened
Am J Clin Pathol 1999; 111:349-351
349
Goldstein et al / FIXATION ARTIFACT
•Table II
In Vitro Unfixed and Fixed Colon Segment Lengths
Segment Length
In vivo
In vitro, fresh state
In vitro, after fixation
Median Length (cm)
Range (SD)
5.00
3.00
2.15
—
1.3-4.6 (0.69)
1.0-3.8(0.61)
but not stretched. The vascular pedicles were ligated, and
the specimen was removed from the patient. The lengths
between each of the sutures were measured after 10 to 20
minutes from the time the specimen was removed from the
patient. During this time, the unfixed specimen was kept in
a specimen container in the operating room. The specimen
was then fixed in 10% neutral buffered formalin for 12 to 18
hours. During fixation, 1 end of the specimen was stretched
and pinned to a wax board such that the distance between
the 2 sutures was again 5.0 cm. The other half of the specimen was allowed to float freely in the formalin-filled
container. The distances between the 2 sutures were
measured after fixation, and the specimen then was processed
in the usual manner.
Results
The bowel segments shrank to a median length of 3.0
cm, or 40% of their original in vivo length after being
removed from the patient and left in an unfixed state for 10
to 20 minutes ITable II. The free-floating ends shrank an
additional 0.85 cm, to a median length of 2.15 cm after
formalin fixation. One specimen had a segment that was 1.0
cm after formalin fixation. Overall after fixation, colon
segments shrank 57% of their original in vivo length. In
contrast, the pinned halves of the specimens almost maintained their original segment length after fixation with a
median value of 4.9 cm (range, 4-5.8 cm). In terms of the
total amount of organ shrinkage, 70% occurred during the
first 10 to 20 minutes after removal from the patient, and the
remaining 30% occurred after fixation. There were no appreciable differences in the amount of organ shrinkage before or
after fixation between specimens with (2.0 cm) and without
diverticular disease (2.4 cm).
Shrinkage (%)
40
57
These shrinkage percentages and time periods during
which they occurred have implications for the accuracy of
in vitro margin lengths when measured by pathologists
compared with the in vivo lengths. If precise margin
measurements are to be obtained, they must be performed
immediately after the specimen has been removed from the
patient. Otherwise, a correction factor of approximately 2x
must be applied when interpreting the margin length. The
difference between the margin lengths of unfixed and fixed
colon specimens is minimal. This shrinkage factor is especially important when dealing with low-rectal adenocarcinomas
because an adequate distal resection margin is considered 1.0
cm in these resection specimens.3
We found only 1 similar study that consisted of 10 specimens.4 The average margin shrank 48% after fixation. In
that study, 73% of the total colon segment shrinkage
occurred after removal of the specimen from the patient, and
the remaining 23% occurred during fixation. The interval
between specimen removal and the measurement of the
unfixed specimen segment was not provided.
Our results contrast with the opinions of the surgeon
Goligher,5 who commented that unlike the surgeons who
stretch the bowel before measuring the margin, he straightened, but did not stretch, the organ before measuring.
Goligher inferred that a 3-cm colon specimen margin in the
unstretched in vivo colon was unchanged in the freshly
measured specimen. 5 These comments were made in
response to statements made in a German study by
Hermanek et al,5 who stated that a 3-cm margin in the fresh
specimen was equivalent to a 5-cm in vivo measurement by
the surgeon. The results of our study support the latter
authors' comments.
From the Departments of 'Anatomic Pathology and ^Colorectal
Surgery, William Beaumont Hospital, Royal Oak, Michigan.
Address reprint requests to Dr Goldstein: Department of
Anatomic Pathology, William Beaumont Hospital, 3601 W
Thirteen Mile Rd, Royal Oak, MI 48073.
Discussion
We found that sigmoid and rectal resection margin
segments shrank 57% after fixation. The majority of the
organ shrinkage occurred within the first few minutes after
removal of the specimen from the patient. Only 30% of the
total shrinkage can be attributed to formalin fixation.
350
Am J Clin Pathol 1999;111:349-351
References
1. Manson PN, Corman ML, Coller JA, et al. Anterior resection
for adenocarcinoma: Lahey Clinic experience from 1963
through 1969. AmJ Surg. 1976;131:434-441.
© American Society of Clinical Pathologists
Anatomic Pathology / ORIGINAL ARTICLE
2. Manson PN, Veidenheimer MC, Coller JA, et al.
Anastomotic recurrence after anterior resection for
carcinoma: Lahey Clinic experience. Dis Colon Rectum.
1976;19:219-224.
3. Vernava AMI, Moran M, Rothenberger DA, et al. A
prospective evaluation of distal margins in carcinoma of the
rectum. Surg Gynecol Obstet. 1992;175:333-336.
© American Society of Clinical Pathologists
4. Weese JL, O'Grady MG, Ottery FD. How long is the five
centimeter margin? Surg Gynecol Obstet. 1986;163:101-103.
5. Goligher J. Incidence and pathology of carcinoma of the
colon and rectum. In: Goligher J, ed. Surgery of the Anus,
Rectum and Colon. London, England: Bailliere Tindall;
1984:426-464.
Am J Clin Pathol 1999;111:349-351
351
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