| Keywords
Rectal Cancer, Rectal Polyp, HNPCC, Rectal
Ulcer
Introduction
A 50 year old man was referred for EUS evaluation
of a rectal cancer following endoscopic polypectomy.
Methods for EUS Capture
EUS was done with a Pentax solid state radial
solid probe at 6.5 mHz using water filled technique. Images
were captured to SVHS tape and digitized using Adobe Premiere
Software.
Case Summary
A 50-year-old male was referred for screening
colonoscopy. His only complaint was rectal discharge that
required him to return to the bathroom ten to fifteen minutes
after a bowel movement. He denied any rectal bleeding or pain.
The patient's past medical history was notable for a transitional
cell carcinoma of the bladder which presented with gross hematuria
at age 46. He had undergone cystoscopic resection and was
being followed with cystoscopic exams every six months and
had no evidence of recurrence. His family history was negative
for colorectal cancer, uterine/ovarian cancer and genitourinary
cancers.
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Figure
2A |
|
Figure
2B: Video clip of EUS showing tumor and
additional hypoechoic area, probably representing an
abnormal lymph node. |
High
Resolution Version
(requires a high bandwidth connection) |
His colonoscopy revealed the presence of
a 2 cm polyp near the first valve of Houston, and smaller
polyps at 70, 60, 45, 35 and 20 cm. The rectal polyp, as partially
removed with a snare, and the pathology revealed a well to
moderately differentiated adenocarcinoma arising in a tubulovillous
adenoma (Figure 1). No lymphatic or vascular invasion was
seen but the tumor extended in multiple fields to the cauterized
polypectomy margins. The smaller polyps were all tubular adenomas.
Rectal EUS was performed two days after
the rectal polypectomy. The EUS suggested this was a T2 lesion
that measured 6 mm in thickness and 2.5 to 3.0 cm in width.
There was no clear space between layer four and the tumor
(Figure 2A,B). Just adjacent to the tumor there was a 5 mm
hypodense area consistent with a small lymph node (Figure
2B). There was approximately 5 cm between the tumor and the
anal verge. A representative corresponding visible human image
is shown in Figure 3, and the approximate location of the
tumor in the interactive visible human database is shown in
Figure 4.
The rectal tumor was evaluated for microsatellite
instability by immunohistochemistry and by PCR. The immunohistochemistry
analysis demonstrated normal hMLH1, hMSH2 and hMSH6 protein
expression. The PCR based assay showed MSI in 6 of 9 markers
tested. Further testing for a mutation in hMSH2 was done on
blood with a conformation sensitive gel electophoresis mutation
scanning technique. Southern blot analysis was also performed
and no mutations could be found in the hMSH2 gene.
After an extensive discussion with the patient
and surgeon regarding his findings and the potential for a
germ-line propensity for cancer, it was elected to proceed
with a total coloectomy and formation of an ileostomy.
Pathology on the surgical specimen revealed
the previous polypectomy site 3.7 cm from the pectinate line
with no residual tumor found (Figure 5A). However, necrosis
was found into the muscularis propria (Fig 5A-C, Muscularis
Propria, Yellow "M"). Ten perirectal lymph nodes
were all negative for metastatic disease. Two 4 mm tubular
adenomas were also found in the resected specimen, one in
the transverse colon the other in the descending colon. The
patient had an uneventful postoperative course.
Discussion
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Figure
5A |
|
Figure
5B |
|
Figure
5C |
EUS is a valuable tool in the staging of
rectal malignancies (1,2). A rather large literature body
exists showing the utility of EUS in directing therapy of
rectal cancer, particularly in determining whether or not
trans anal local resection can be utilized for small tumors,
or whether more aggressive neoadjuvant therapy is needed for
advanced lesions (1-4).
Studies on the accuracy of EUS have focused
primarily on the T and N staging of tumors at the time of
diagnosis. The depth of invasion (T stage) is generally felt
to be about 90% accurate for EUS, and for nodal status about
80% accurate (5).
Pitfalls regarding EUS staging involve many
technical issues, such as position of the probe, endoluminal
artifacts, peritumoral inflammation, desmoplastic changes,
and post biopsy changes (6,7)
Inflammation, as occurs after polypectomy,
can disrupt the echolayers of the bowel wall, and negatively
impact EUS staging. To address the effect of polypectomy on
staging, Kruskal et al. evaluated 18 patients who had malignant
polyps and who were then staged by EUS for residual tumor
(8). The accuracy of EUS was much less than what was seen
in previous studies evaluating T-stage (5). Although Kruskal
et al reported a sensitivity of 100% for finding residual
disease, their specificity was only 44%. They still conclude
that EUS is useful in staging surgery.
Our case visually demonstrates inflammatory
artifact than mimics tumor. Had the EUS abnormalities been
confined to the submucosa, one could have considered a trans
anal approach to managing the positive margins of this endoscopically
resected tumor. However, this case was somewhat complicated
by the presence of a probable genetic cancer syndrome and
patient wishes for an aggressive surgical approach.
This case illustrates a potential pitfall
in staging rectal tumors following polypectomy. We recommend
EUS staging be performed prior to polypectomy for potentially
malignant rectal polyps for more accurate staging and to assess
the feasability of endoscopic management. For polyps which
have been removed and in which cancer has been found, one
should consider marking the area with india ink and performing
EUS after healing of the polypectomy ulcer.
References
1. Saitoh N, Okui K, Sarashina H, Suzuki
M, Arai T, Nunomura M Evaluation of echographic diagnosis
of rectal cancer using intrarectal ultrasonic examination
Dis Colon Rectum 1986 Apr;29(4):234-42
2. Lindmark G, Elvin A, Pahlman L, Glimelius B. The value
of endosonography in preoperative staging of rectal cancer
Int J Colorectal Dis 1992 Sep;7(3):162-6
3. Marone P, Petrulio F, de Bellis M, Battista Rossi G, Tempesta
A Role of endoscopic ultrasonography in the staging of
rectal cancer: a retrospective study of 63 patients J
Clin Gastroenterol 2000 Jun;30(4):420-4
4. Hildebrandt U, Feifel G Importance of endoscopic ultrasonography
staging for treatment of rectal cancer Gastrointest
Endosc Clin N Am 1995 Oct;5(4):843-9
5. Herzog U, von Flue M, Tondelli P, Schuppisser JP How
accurate is endorectal ultrasound in the preoperative staging
of rectal cancer Dis Colon Rectum 1993 Feb;36(2):127-34
6. Kruskal JB, Kane RA, Sentovich SM, Longmaid HE Pitfalls
and sources of error in staging rectal cancer with endorectal
us Radiographics 1997 May-Jun;17(3):609-26
7. Akasu T, Sugihara K, Moriya Y, Fujita S Limitations
and pitfalls of transrectal ultrasonography for staging of
rectal cancer Dis Colon Rectum 1997 Oct;40(10
Suppl):S10-5
8. Kruskal JB, Sentovich SM, Kane RA Staging of rectal
cancer after polypectomy: usefulness of endorectal US
Radiology 1999 Apr;211(1):31-5
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