Inflammatory Polyps, Inflammatory Cap Polyps and Polypoid Mucosal Prolapse

Inflammatory polyps are the most common type of polyp in Inflammatory bowel disease. These polyps usually occur in patients with moderate to severe colitis but persist in patients with quiescent disease.
Inflammatory polyps also occur in association with Crohn's disease and other inflammatory disorders of the GI tract such as ischemic colitis or infectious colitis. These polyps may occur in infective conditions such as amoebiasis, schistosomiasis and bacillary dysentery.
A special form of inflammatory polyp develops in the colon at the site of ureteric implantation where probably due to chemical irritation there is localized expansion of lamina propria and cystic dilatation of glands.
In order to determine the underlying disease it is necessary to examine non-polypoid mucosa, which should be biopsied at the same time.

Formation of inflammatory polyps:

These are developed as a regenerative response to localized or diffuse inflammation and ulceration of the mucosa followed by regeneration of the intervening non-ulcerated epithelium. Eventually the regenerated mucosa become completely re-epithelized and persists above the level of the surrounding mucosa as inflammatory polyps.
Sometimes inflammatory polyps represent spared mucosa surrounding areas of deep ulceration.
Some polyps decrease in size , most remain stable a few may continue to grow if they undergo torsion or prolapse.

Gross:

May be sessile, pedunculated or may consist of long finger-like projection referred to as 'filliform'. These polyps may be single or numerous in number and the size range between 0.5 - 1.0 cm.
'Giant Inflammatory polyps' may cause bleeding, obstruction, prolapse or intussusception.

Histopathological features:

- The inflammatory polyps are characterized by :

Inflamed lamina propria ; distorted colonic epithelium - tortuous, branched, elongated and cystic crypts; surface erosion ; congestion ; haemorrhage ; crypt abscesses.

- In some cases pseudosarcomatous changes are noted characterized by :

Enlarged spindle or epithelioid shaped multinucleated bizarre stromal cells.; present at the surface of ulcerated polyp.

[ D/D - Sarcoma ; 1) These lesions lack atypical mitosis 2) Located within granulation tissue and below areas of ulcerataion 3) Positive for endothelial & myofibroblastic markers].

- Rarely dysplasia or carcinoma may develop in inflammatory polyps. However, the risk of developing dysplasia is very low and these polyps are not considered pre-neoplastic lesions. ImageLink

Inflammatory cap polyps:

Images:

Inflammatory cap polyps are defined as an inflammatory polyp either with or without prolapse-related changes that contain an overlying 'cap' of necroinflammatory debris and granulation tissue.
These inflammatory polyps may develop in inflammatory bowel disease either primarily or secondarily as a result of peristalsis or trauma induced mucosal prolapse. This may lead to traction & twisting of polyps causing localized ischemic damage, regeneration & repair of the lamina propria & epithelium & the development of an inflammatory polyp. There may be associated diverticular disease.
These polyps are usually isolated lesions, but can be numerous in number -( 'cap polyposis').
Cap polyps are usually located in the sigmoid colon & rectum of adults. These are sessile haemorrhagic polyps, present on the crest of mucosal folds and are less than 1 cm in diameter.
The patients present with rectal bleeding & mucous diarrhea.
In some cases these are also seen in the small intestine complicating carcinoid tumour.

Polypoid mucosal prolapse:

- Classical solitary ulcer(mucosal prolapse) can be polypoid.
- May be present in diverticular disease on the apices of mucosal folds.
- Subsequent to previous surgery (Eg: stomas or pelvic ileal reservoir)
- Inflammatory Cloacogenic polyps- At the anorectal junction. There is florid villiform epithelial hyperplasia. Associated with haemorrhoids and pelvic descent syndromes.
- Inflammatory Myoglandular polyps- Usually in sigmoid colon.