Practical Gastrointestinal Endoscopy

162
CHAPTER 6
Apart from lipomas or shiny, worm-like inflammatory polyps,
which sometimes have a cap of white slough, all other polyps are
usually best removed. Macroscopic differentiation is inaccurate
and there is no sure way of anticipating which polyp will prove
histologically to be premalignant.
A malignant polyp may be obviously irregular, may bleed easily
from surface ulceration or be paler, and also firmer than usual to
palpation with the biopsy forceps. Such signs of possible malignancy
in a stalked polyp warn the endoscopist to electrocoagulate
the base thoroughly, to obtain a histological opinion on the
stalk and to localize and tattoo the polyp carefully for follow-up
and in case subsequent surgery is indicated.
Carcinomas are usually very obvious. They are larger and
have a more extensive irregular base; carcinomatous ulcers are
uncommon in the colon but look like malignant gastric ulcers.
However, small ‘early cancers’ do occur, typically 6–8·cm in diameter
with a slightly depressed center. Conditions which can
almost exactly mimic malignancy are granulation tissue masses
at an anastomosis, larger granulation tissue polyps in chronic
ulcerative colitis, and (rarely) the acute stage of an ischemic
process. Biopsy evidence should always be obtained, bearing in
mind that the pathologist may only be able to report ‘dysplastic
tissue’ since there may not be diagnostic evidence of invasive
malignancy in the small pieces presented, which is why either
a large-forceps biopsy or snare-loop specimen should be taken
whenever possible. Even with standard forceps, a surprisingly
large specimen can be taken by the ‘avulsion’ or ‘push biopsy’
approach; the instrument is then withdrawn keeping the forceps
outside the tip so as not to shear off parts of the tissue by pulling
it back through the biopsy channel.
Inflammatory bowel disease
Biopsies must always be taken in any patient with bowel frequency,
loose stools or any clinical suspicion of inflammatory disease.
‘Microscopic colitis’, whether ulcerative or Crohn’s, which is
clearly abnormal on microscopy, can look absoloutely normal to
the endoscopist. The possibly related condition of ‘collagenous
colitis’, a rare cause of unexplained diarrhea due to an extensive
‘plate’ of collagen under the epithelial surface, also shows normal
mucosa visually and the diagnosis can only be made histologically.
Mucosal abnormality can vary enormously in different forms
of inflammatory bowel disease. Inflamed mucosa can show the
most minute haziness of vascular pattern, slight reddening or
tendency to friability. Colonoscopic biopsies unfortunately
rarely yield diagnostic granulomas in Crohn’s disease, whereas
the appearance of multiple, small, flat or volcano-like ‘aphthoid’
ulcers set in a normal vascular pattern is characteristic. The