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  • Surgical Pathology Criteria

    Mucosal Prolapse / Cloacogenic Polyp


    • Histopathologic features of rectal mucosal prolapse ranging from ulceration to polyp formation

    Alternate/Historical Names

    • Cap polyposis
    • Hamartomatous inverted polyp
    • Inflammatory cloacogenic polyp
    • Localized colitis cystica profunda
    • Solitary rectal ulcer syndrome

    Diagnostic Criteria

    • A variety of changes may be seen secondary to rectal mucosal prolapse
      • Usually on anterior rectal wall within 12 cm of anal verge
      • May occur in sigmoid or higher or in stomas
    • Superficial ulceration or erosion of mucosa
      • May form a pseudomembrane
      • Capillary congestion and thrombosis usually present
      • Ulcers may be multiple
    • Granulation tissue in high lamina propria
    • Thickened, disorganized muscularis mucosae with extension into lamina propria
      • Smooth muscle surrounds individual crypts
      • Elastosis may also surround crypts
        • Not normally present in lamina propria
    • Crypts may be elongated and straight or markedly distorted
      • May show cystic dilation
      • May be serrated
      • May form villiform hyperplasia
    • Glands may be displaced into submucosa
      • Has been termed localized colitis cystica profunda
      • Lamina propria may accompany glands
      • May simulate invasive carcinoma
    • Mucus extravasation into stroma may be present
      • May extend into lamina propria or submucosa
    • Regenerating mucosal epithelium may appear adenomatous
      • Adenomatous appearance is most marked in deep glands
        • Maturation at surface is present, if not completely eroded
      • Rare cases of prolapse apparently secondary to an adenoma
    • Cloacogenic polyp refers to a combination of the above features that gives rise to an inflammatory reactive polyp that appears hamartomatous (because of the mixture of glands and muscle)
      • Present in up to ¾ of cases
    • Cap polyposis has been described in a few reports
      • May represent numerous small prolapse polyps
      • Located on edges of rectal mucosal folds

    Robert V Rouse MD
    Department of Pathology
    Stanford University School of Medicine
    Stanford CA 94305-5342

    Original posting / last update: 12/27/09 1/31/16

    Supplemental studies


    • Smooth muscle actin stain shows thickened, distorted muscularis mucosae
      • Extends into lamina propria
      • Surrounds individual glands
    • Elastin stain shows similar features
      • Not normally present in lamina propria

    Differential Diagnosis

    Mucosal Prolapse / Cloacogenic Polyp Peutz-Jeghers Polyp
    Usually solitary polyp Usually multiple
    Smooth muscle surrounds individual crypts Prominent arborizing smooth muscle bundles surround groups of crypts
    Polyps rare in small intestine Most polyps in small intestine
    Not associated with oral pigmentation Associated with oral pigmentation
    Usually eroded surface Erosion infrequent


    Mucosal Prolapse / Cloacogenic Polyp Colorectal Adenoma
    Nuclear atypia most prominent deep in the lesion with surface maturation Nuclear atypia involves surface of polyp
    Nuclei usually enlarged but round and not stratified and not densely packed Nuclei elongated, hyperchromatic, densely packed and frequently stratified
    Apoptosis not prominent Prominent apoptosis


    Mucosal Prolapse / Cloacogenic Polyp Sporadic Juvenile Polyp
    Surface erosions with granulation tissue frequent Surface erosions infrequent
    Irregular glands with scattered dilation Prominent, regularly dilated glands
    Smooth muscle extension into lamina propria of polyps No prominent smooth muscle in lamina propria of polyps
    Most in rectum or sigmoid May involve any part of colorectum


    Mucosal Prolapse / Cloacogenic Polyp Cowden Disease, Colorectal Polyp
    Surface erosions with granulation tissue frequent Surface erosions infrequent
    Polypoid Sessile
    Prominent smooth muscle extension into lamina propria of polyps Smooth muscle in lamina propria usually not promiinent
    No associated lesions Most have facial and oral papillomas, fibromas and skin tumors, see description LINK
    No genetic abnormality PTEN mutations in 80%


    Mucosal Prolapse / Cloacogenic Polyp Reactive / Inflammatory Polyp
    Smooth muscle extension into lamina propria of polyps No smooth muscle in lamina propria of polyps
    Usually localized to rectum Usually multiple, may involve any inflamed area
    Not associated with inflammatory bowel disease Usually associated with ulcerative colitis but may be sporadic


    Mucosal Prolapse / Cloacogenic Polyp GI Perineurioma
    Fibrovascular stroma Lacks vascularity
    Inflammatory infiltrate Inflammation infrequent
    Prominent gland component Mostly a spindled stromal lesion, crypts pushed aside
    Villiform eroded surface Surface intact and normal
    Smooth muscle extends into lamina propria around crypts Lamina propria spindled lesion is smooth muscle actin negative and positive for perineurial markers


    Mucosal Prolapse / Cloacogenic Polyp (Localized Colitis Cystica Profunda) Invasive Colorectal Adenocarcinoma
    No surface carcinoma component Surface component usually present
    No high grade nuclear atypia High grade nuclear atypia usually present
    No cribriform glands or complex architecture Complex architecture with cribriform glands frequent
    No desmoplastic stromal response Desmoplastic stromal response
    Lamina propria may accompany displaced glands No lamina propria accompanying invasive glands
    Mean age 35 years Occurs in older patients


    Mucosal Prolapse / Cloacogenic Polyp (Solitary Rectal Ulcer) Crohn Disease
    Shallow ulceration Deep ulcers and fissures
    Restricted to rectum (rarely in sigmoid) May involve any part of GI tract


    Mucosal Prolapse / Cloacogenic Polyp (Solitary Rectal Ulcer) Ulcerative Colitis
    Usually a localized lesion Usually a diffuse lesion
    Adjacent, intervening mucosa normal Adjacent, intervening mucosa inflamed
    Restricted to rectum (rarely in sigmoid) May involve longer segments of colon


    • Mean age 35 years
      • May occur in children
    • Probably due to excess straining during defecation
      • Frequent history of constipation or diarrhe
    • Frequently presents with hematochezia
    • Endoscopy may show ulcer(s) or polyp or granular mucosa


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    • Ortega AE, Klipfel N, Kelso R, Petrone P, Román I, Díaz A, Avalos B, Kaufman HS. Changing concepts in the pathogenesis, evaluation, and management of solitary rectal ulcer syndrome. Am Surg. 2008 Oct;74(10):967-72.
    • Felt-Bersma RJ, Stella MT, Cuesta MA. Rectal prolapse, rectal intussusception, rectocele, solitary rectal ulcer syndrome, and enterocele. Gastroenterol Clin North Am. 2008 Sep;37(3):645-68.
    • Parfitt JR, Shepherd NA. Polypoid mucosal prolapse complicating low rectal adenomas: beware the inflammatory cloacogenic polyp! Histopathology. 2008 Jul;53(1):91-6.
    • Singh B, Mortensen NJ, Warren BF. Histopathological mimicry in mucosal prolapse. Histopathology. 2007 Jan;50(1):97-102
    • Shaco-Levy R, Jasperson KW, Martin K, Samadder NJ, Burt RW, Ying J, Bronner MP. Morphologic characterization of hamartomatous gastrointestinal polyps in Cowden syndrome, Peutz-Jeghers syndrome, and juvenile polyposis syndrome. Hum Pathol. 2016 Mar;49:39-48. doi: 10.1016/j.humpath.2015.10.002. Epub 2015 Oct 31. PubMed PMID: 26826408..
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