Small and diminutive colorectal polyps

Research paper
J Interv Gastroenterol 5:1, 32-34; January/February/March 2015; © 2015 Journal of Interventional Gastroenterology
Small and diminutive colorectal polyps: risk of
malignancy
Anish V. Patel1, David Padua2, Michael Lewis3, Hartley Cohen4, Felix W. Leung4
Division of Internal Medicine, Cedars Sinai Medical Center, Los Angeles, CA, USA; 2UCLA Training Program in Digestive Diseases, Los Angeles, CA, USA; 3Division of Pathology,
Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, USA; 4Division of Gastroenterology, Veterans Affairs Greater Los Angeles Healthcare System, Los
Angeles, CA, USA
1
Key words: small polyps, diminutive polyps, colorectal cancer, polypectomy
Abbreviations: CT, computed tomography; CEA, carcino embryonic antigen
Introduction
The prevalence of advanced histological features in diminutive
(≤5 mm) and small (6-9 mm) colon polyps is low, and they are
considered to have low potential for malignant transformation.1,2
Performing a polypectomy increases the costs associated with
a colonoscopy as well as the risk of complications.3,4 Newer
diagnostic techniques have prompted the approach of ‘predict,
resect and discard’ for diminutive and small polyps, a strategy
whereby real time diagnosis of polyps would serve as a substitute
for histopathological diagnosis to reduce costs.5-9
Case report
We present a 73-year old Caucasian male with history of
hypertension but no family history of colon cancer. On routine
screening colonoscopy, he was found to have 5 mm diminutive
polyp in the proximal colon that was biopsied (Fig. 1). Pathology
returned as invasive adenocarcinoma (Fig. 2). A follow up
surveillance colonoscopy in two weeks revealed a 7 mm small polyp
at the site of the previous biopsy. Polypectomy was performed by
hot snare (Fig. 3). Pathology revealed the margins were positive
for malignancy (Fig. 4). CT scan of the abdomen & pelvis was
negative for metastases, with no pelvic lymphadenopathy. CEA
level was 0.87 (within normal limits). He was then referred to
Colorectal Surgery and underwent an uncomplicated right
hemicolectomy. The surgical specimen had normal margins with
no residual malignancy, and the 12 pericolonic lymph nodes were
negative for metastases.
Figure 1. First screening colonoscopy showed a 5 mm diminutive polyp
in the proximal colon.
Discussion
In a data mining study, the authors noted that prevalence of
advanced histology in small polyps has become a crucial issue
in optimizing colorectal cancer screening strategies, especially in
view of the advent of computed tomography colonography. Data
were reviewed retrospectively from 3291 colonoscopies performed
*Correspondence to: Felix W. Leung; Email: felix.leung@va.gov
Submitted: Sep/10/2014; Revised: Sep/20/2014; Accepted: Sep/24/2014
DOI: 10.7178/jig.166
32
Figure 2. Histopathological examination of the forcep biopsy of the
diminutive polyp on the first screening colonoscopy showed invasive
adenocarcinoma.
J Interv Gastroenterol
Volume 5 Issue 1
CASE REPORT
Research paper
Figure 3. Follow up surveillance colonoscopy showed a 7 mm small
polyp in the proximal colon.
Figure 4. Histopathological examination of the small polyp removed by
hot snare polypectomy showed invasive adenocarcinoma, with margins
that were positive for malignancy.
on asymptomatic patients found to have an adenoma on screening
with flexible sigmoidoscopy a few weeks before the colonoscopy
or who had a family history of colorectal cancer. All polyps were
excised endoscopically and sent for pathology testing. Specimens
with advanced histology were confirmed by a second reading. Of
the 3291 colonoscopies performed, 1235 colonoscopies yielded a
total of 1933 small or diminutive adenomatous polyps. Advanced
histology including carcinoma was found in 10.1% of small (510 mm) adenomas and in 1.7% of diminutive adenomas (≤4
mm). Carcinoma was found in 0.9% of small adenomas, and
0% of diminutive adenomas. Adenomas 5-10 mm in size harbor
pathologically significant histology, and the need for removal
of these lesions must be addressed to optimize colorectal cancer
prevention.1
In another recent review, routinely processed specimens from
20 patients (Male/Female ratio: 13/7; mean age: 65 yr) with small
apparently de novo invasive colorectal adenocarcinomas (all ≤1.0
cm in size) were evaluated. These were present in the right colon
in 5% of these cases. Their mean size was 7 mm (range: 3 to 10
mm). All cases were stage T1 and the majority were moderately
differentiated (75%). Of these 20 cases, only 1 (5%) patient had
lymph node metastases. Upon complete sectioning of the tissue
blocks of tumor, residual foci of adenomatous epithelium were
present in 16/20 (80%) cases, of which 75% contained foci of
high-grade dysplasia. Only 2 patients (10%) developed visceral
metastases upon follow-up. Thus, true small de novo colorectal
adenocarcinomas, tumors that lack an identifiable adenomatous
component, are rare, because complete tissue sectioning reveals
residual adenomatous tissue in the majority of cases. The biologic
characteristics and natural history of small carcinomas with a
minimal dysplastic component, and those with no identifiable
adenomatous component, are similar to conventional large (>1
cm) adenocarcinomas. The authors suggested that the de novo
invasive colorectal adenocarcinomas should probably be treated
similarly. Our patient underwent a right hemicolectomy and
exploration showed no metastatic lesions.2
The effective use of the ‘predict, resect and discard’ strategy is
dependent on the accuracy of in vivo determining of histology and
advanced histological features in adenomas. The literature proposes
that after prediction of non-neoplastic features on visualization,
a polyp can be discarded.10-12 The patient in our case did not
undergo a ‘predict’ step of endoscopic assessment. And had the
polyp been discarded, the positive margins of the resected polyp
would not have been identified, and he would not have undergone
a “curative” colon resection. The malignant small polyp that was
found in our patient would indicate that the practice of ‘resect
and discard’ for small polyps may not be wise for this and similar
patients. This case illustrates that in the absence of maneuvers to
predict the neoplastic nature of the polyp, the ‘discard’ strategy
simply based on size alone may not be appropriate. Advances in
imaging technology with high accuracy of prediction, however,
may provide support for such a strategy.12,13
Diminutive polyps (≤5 mm) are not routinely reported in
computed tomography colonography and subsequently not
referred for colonoscopy due to the very low likelihood of advanced
neoplasia and the high costs associated with polypectomy.14-16
Such a strategy also would have left our patient with a “treatable”
colon cancer in place.
www.jigjournal.org
Conclusion
The prevalence of advanced histological features in small and
diminutive polyps is low, but they do carry a risk of malignancy.
This has important implications for the practices of colonoscopy
and polyp removal. The application of “predict, resect and discard”
strategies on the basis of polyp size requires careful consideration
of potential malignant features and accurate and reproducible
diagnostic criteria. The push to reduce costs associated with
J Interv Gastroenterol
33
histopathological examination may nullify the benefits derived
from the approach adopted in the current patient.
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