A 28-year-old female presented with occasional streaks of
bright red blood in her stools. On further questioning the patient gave the history of frequent episodes
of constipation. Proctosigmoidoscopic examination revealed two shallow ulcers in a nodular area of the
anterior wall of the rectum at 8 cm. This area was biopsied and interpreted as adenocarcinoma arising
from a tubular adenoma. A resection was subsequently performed and representative sections of this
lesion are submitted for your review.
Case 3 - Figure 1 - A low power view of eroded rectal mucosa with crypts entrapped in disorganized fibromuscular stroma.
Case 3 - Figure 2 - Rectal mucosa with crypts lined by regenerative epithelium. There is adjacent erosion and a fibrinopurulent cap. Displaced groups of hypermucinous crypts are present in the submucosa.
Case 3 - Figure 3 - Same features as in Slide 2 under higher power.
Case 3 - Figure 4 - Large mucin-filled submucosal cystic spaces partially lined by simple columnar to cuboidal epithelium (colitis cystica profunda).
The crypts are separated by a proliferation of
fibromuscular tissue arising perpendicularly from a thickened and frayed muscularis mucosae. The crypts
show regenerative features including crypt branching and goblet cell depletion along with crowding,
increased basophilia and enlargement of the epithelial nuclei. The mucosa is extensively eroded and, in
some areas, covered by fibrinopurulent exudate. The submucosa is fibrotic. Downwardly displaced groups
of crypts are found in the submucosa, as are cystic, mucin-filled spaces partially lined by epithelium.
Solitary Rectal Ulcer Syndrome with Localized Colitis Cystica Profunda
"Solitary rectal ulcer syndrome" (SRUS) describes a
clinicopathologic entity with a characteristic, but not specific histologic appearance. The term is
actually a misnomer since the lesions of SRUS may be multiple and may or may not include an ulcer. In
its classic sense, SRUS occurs in the mid-rectum. SRUS most often occurs in young adults (mean age about
35 years) and is slightly more common in women. The most common presenting symptoms are passage of fresh
blood and mucus, diarrhea or constipation, tenesmus, and straining with defecation. Characteristic
histologic findings include: hypertrophic, disorganized muscularis mucosae with bundles of smooth muscle
and collagen extending into the superficial lamina propria around crypts; diffuse fibrosis of the lamina
propria; distortion of crypt architecture; crypt and surface epithelium that is often hyperplastic or
shows regenerative atypia; and erosions with or without adherent exudates. Endoscopically, the majority
of erosions/ulcerations occur on the anterior or anterolateral rectal wall 7-10 cm from the anal margin
with diameters up to 5 cm and may be covered by a white slough. They are usually flat, well demarcated
lesions with an irregular shape. Polyps and sessile plaques may accompany or occur without ulcers.
Sometimes the only endoscopic finding is hyperemia or a granular appearing mucosa. The surrounding
mucosa is often hard and lumpy. Similar lesions found in the anal transitional zone are called
inflammatory cloacogenic polyps. Some prefer not to divide such lesions by site or minor histopathologic
differences and would rather classify all such polypoid lesions as "prolapse-induced inflammatory polyps"
or "mucosal prolapse syndrome." As in other polypoid lesions, the mucosal epithelium may become
displaced into the submucosa. When these submucosal elements take the form of cystic, mucin-filled
spaces with or without an epithelial lining, it is referred to as colitis/proctitis cystica profunda.
Colitis cystica profunda is reported in about 10-30% of patients with SRUS. These cystic spaces may form
intramural masses several centimeters in diameter, and may be firm due to the presence of dystrophic
calcification of the mucin. Colitis cystica profunda is not unique to SRUS. It can occur in a more
diffuse fashion in association with other types of mucosal damage such as infection or idiopathic
inflammatory bowel disease.
Pathogenesis: Most cases of solitary rectal ulcer syndrome appear to be due to localized mucosal
prolapse. The mucosal prolapse that occurs during excessive straining with defecation is seen as an
attempt to overcome an abnormality of the pelvic floor musculature during defecation, namely,
inappropriate contraction of the puborectalis muscle and the external anal sphincter instead of
relaxation. Repeated trauma of the prolapsing mucosa against the contracting puborectalis muscle and
mucosal ischemia due to the high intrarectal pressures necessary for voiding act together to cause
mucosal damage and eventual ulceration. Mucosal prolapse can be demonstrated in about 85-95% of patients
with SRUS. It is often internal and occult, so that the patient may not even be aware of it. Mucosal
prolapse might likewise go unrecognized by the examining physician unless the patient is asked to perform
a Valsalva maneuver while the mucosa is examined proctoscopically or unless defecatory radiographic
studies are performed.
Treatment: Therapy includes conservative measures such as biofeedback defecation retraining and
increased dietary fiber. When these measures are unsuccessful, surgical procedures to repair the
prolapsed rectum, such as rectopexy or insertion of a perianal nylon loop, should be considered. Most
polyps may be safely removed by endoscopic polypectomy.
When palpated on physical exam, SRUS not
uncommonly gives the impression of a neoplasm or Crohn disease. Histologically, its regenerative
epithelium is often mistaken for dysplastic epithelium and the lesion is diagnosed as an adenoma. Also,
villiform change can occur in the polypoid mucosa giving the false impression of a villous adenoma. The
most important pitfall to avoid is interpreting the atypical appearing crypts surrounded by fibromuscular
lamina propria as invasive adenocarcinoma, as occurred in this case. The presence of colitis cystica
profunda may enhance this appearance or even suggest mucinous adenocarcinoma. However, unlike dysplastic
epithelium, the epithelium of SRUS lacks prominent nuclear stratification and shows maturation toward the
mucosal surface. The submucosal cysts are lined by cytologically bland epithelium. Also, the submucosa
lacks a desmoplastic stromal reaction that almost always accompanies invasive carcinoma of the rectum.
It is also important to remember that invasive carcinoma can occur in an area with prolapse changes.
Colitis cystica profunda is almost always limited to the submucosa. If mucin lakes are in the muscularis
propria, carcinoma is more likely.
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