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Hyperplastic Polyp of the Colon and Rectum

Definition

  • Cytologically bland lesion with regular, elongated serrated crypts

Alternate/Historical Names

  • Microvesicular hyperplastic polyp

Covered Separately

Diagnostic Criteria

  • Upper (luminal) portion of polyp has a “saw tooth” appearance
    • Formed by tufts or folds of abundant apical cytoplasm
    • Cross-sections of glands have a star-shaped lumen
    • Nuclei are small, regular, round and basal in luminal half of crypt
      • Best evaluated on or near the luminal surface
  • Crypts are elongated but straight, narrow and hyperchromatic at the base
    • Base of crypts shows proliferative changes
      • Proliferative zone on Ki67 stain expanded to basal 1/3 to ½ of crypt
      • Nuclei enlarged
      • Nucleus/cytoplasm ratio elevated
        • The deep proliferative zones of hyperplastic polyps and reactive processes closely mimic adenomatous changes
    • All crypts reach to the muscularis mucosae
  • Basement membrane is frequently thickened
  • Cytoplasm defines three types of hyperplastic polyp:
    • Microvesicular mucin rich type (most common)
    • Goblet cell rich type (poorly defined)
    • Mucin poor type, with eosinophilic cytoplasm (rare)
    • No clear significance to these types
  • CK20 positive zone expanded to luminal ½ or 2/3
  • Irregular changes in architecture are not present including
    • Dilation of crypts
    • Branching
    • Horizontal glands at base
    • Mature mucinous cells at base of crypts
    • Presence of any of these suggests sessile serrated adenoma
  • Nuclear dysplasia is not permitted for the diagnosis of hyperplastic polyp
  • Usually small sessile left sided lesions
  • Either of the following features should raise the possibility of sessile serrated adenoma
    • Size ≥0.5 cm
    • Right sided lesion
    • If both are present, it is almost always a SSA
  • Infrequent epithelial misplacement into submucosa has been described
    • Has also been termed inverted hyperplastic polyp
    • Mucin depleted epithelium similar to basal 1/3 of polyp
    • Accompanied by lamina propria
    • Continuous with overlying polyp through a gap in the muscularis mucosae
      • May require multiple levels to demonstrate
    • Adjacent hemorrhage and hemosiderin common
    • Collagen type IV stain demonstrates strong continuous staining around nests
    • Apparently restricted to sigmoid and rectum
  • Hyperplastic polyps may be associated with perineurioma
    • No clinical significance
  • Hyperplastic polyposis (serrated polyposis)
    • Originally defined by the number and location of hyperplastic polyps
  • Robert V Rouse MD
    Department of Pathology
    Stanford University School of Medicine
    Stanford CA 94305-5342

    Original posting/updates: 1/31/2010, 3/28/11, 11/12/11, 3/20/13

Supplemental studies

Immunohistology

  • Staining is not generally needed for the diagnosis
  • MUC6 completely negative
  • MLH1 stain typically positive

  Ki67 CK20
Normal mucosa Limited to basal ¼ Limited to surface
Hyperplastic polyp Expanded to basal 1/3-1/2 Expanded to luminal 1/2-2/3
SSA Patches of staining at all levels Patches of staining at all levels
TSA Mainly localized to ectopic crypts Irregular staining of luminal surface
Usual adenoma High overall Random
(based on Torlakovic 2008)

Genetic Analysis

  • Genetic studies not generally used for diagnosis
  • MSI normal or low
  • KRAS (microvesicular polyps) or BRAF (goblet cell rich polyps) mutations are frequently present
    • This is not generally needed for the diagnosis
  • CpG island DNA hypermethylation may be present
    • Involving MGMT (26%) and MLH1 (40%) (in microvesicular type HP)
  • Infrequent APC and p53 mutations

Differential Diagnosis

Hyperplastic Polyp Tubular Adenoma
Lacks cytologic dysplasia Requires cytologic dysplasia
Proliferative zone restricted to base Proliferative zone starts at the surface
Gland lining cells mature at the surface No surface maturation
Deep proliferative zone of HP can resemble TA; the surface must be examined to make the distinction in many cases

 

Hyperplastic Polyp Sessile Serrated Polyp / Adenoma
≥90% of bases of crypts straight, regular, narrow, frequently pointed, no dilated flattened bases 1 to 3 crypts required with basal dilation and flattening, bases boot or inverted T shaped, <90% of bases are narrow
Proliferative zone reliably restricted to base Bases contain mature mucous cells
Serrations and CK20+ maturation limited to luminal 2/3 of crypt Serrations and CK20+ patches of maturation can be seen at all levels
Predominantly left sided and small Predominantly right sided and frequently ≥1 cm
Polyps with mixed or intermediate features are designated indeterminate (e.g. between 50-90% narrow crypts and/or <3 flat crypt bases)

 

Traditional Serrated Adenoma Hyperplastic Polyp
Cytologic dysplasia throughout Lacks cytologic dysplasia
Typically complex architecture Crypts are vertically arranged and not complex
Multiple ectopic crypt foci (short disoriented crypts not reaching the muscularis mucosae) Crypts each span from lumen to muscularis mucosae

 

Sporadic Juvenile Polyp Hyperplastic Polyp
Prominent cystically dilated glands Cystic dilation not prominent
Irregular glands Glands are vertically arranged and not complex

 

Hyperplastic Polyp with Mucosal Entrapment (Inverted Hyperplastic Polyp) Mucosal Prolapse / Cloacogenic Polyp
Lacks surface erosion Surface erosions with granulation tissue frequent
No smooth muscle extension into lamina propria Smooth muscle extension into lamina propria of polyps
Lacks regenerative change May have regenerative change in epithelium of polyp

Clinical

  • Not considered to be significant precursors of carcinoma
  • Not considered to justify increased followup or screening

Bibliography

  • Bosman FT, Carneiro F, Hruban RH, Thiese ND (Eds). WHO Classifiication of Tumors of the Digestive System, IARC, Lyon 2010
  • East JE, Saunders BP, Jass JR. Sporadic and syndromic hyperplastic polyps and serrated adenomas of the colon: classification, molecular genetics, natural history, and clinical management. Gastroenterol Clin North Am. 2008 Mar;37(1):25-46
  • Snover DC, Jass JR, Fenoglio-Preiser C, Batts KP. Serrated polyps of the large intestine: a morphologic and molecular review of an evolving concept. Am J Clin Pathol. 2005 Sep;124(3):380-91.
  • Li SC, Burgart L. Histopathology of serrated adenoma, its variants, and differentiation from conventional adenomatous and hyperplastic polyps. Arch Pathol Lab Med. 2007 Mar;131(3):440-5.
  • Sandmeier D, Seelentag W, Bouzourene H. Serrated polyps of the colorectum: is sessile serrated adenoma distinguishable from hyperplastic polyp in a daily practice? Virchows Arch. 2007 Jun;450(6):613-8.
  • Owens SR, Chiosea SI, Kuan SF. Selective expression of gastric mucin MUC6 in colonic sessile serrated adenoma but not in hyperplastic polyp aids in morphological diagnosis of serrated polyps. Mod Pathol. 2008 Jun;21(6):660-9.
  • Yantiss RK, Goldman H, Odze RD. Hyperplastic polyp with epithelial misplacement (inverted hyperplastic polyp): a clinicopathologic and immunohistochemical study of 19 cases. Mod Pathol. 2001 Sep;14(9):869-75.
  • Farris AB, Misdraji J, Srivastava A, Muzikansky A, Deshpande V, Lauwers GY, Mino-Kenudson M. Sessile serrated adenoma: challenging discrimination from other serrated colonic polyps. Am J Surg Pathol. 2008 Jan;32(1):30-5.
  • Torlakovic EE, Gomez JD, Driman DK, Parfitt JR, Wang C, Benerjee T, Snover DC. Sessile serrated adenoma (SSA) vs. traditional serrated adenoma (TSA). Am J Surg Pathol. 2008 Jan;32(1):21-9.
  • Agaimy A, Stoehr R, Vieth M, Hartmann A. Benign serrated colorectal fibroblastic polyps/Intramucosal perineuriomas are true mixed epithelial-stromal polyps (hybrid hyperplastic polyp/mucosal perineurioma) with frequent BRAF mutations. Am J Surg Pathol. 2010 Nov;34(11):1663-71.
  • Rex DK, Ahnen DJ, Baron JA, Batts KP, Burke CA, Burt RW, Goldblum JR, Guillem JG, Kahi CJ, Kalady MF, O'Brien MJ, Odze RD, Ogino S, Parry S, Snover DC, Torlakovic EE, Wise PE, Young J, Church J. Serrated lesions of the colorectum: review and recommendations from an expert panel. Am J Gastroenterol. 2012 Sep;107(9):1315-29
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