Stanford School of Medicine

Surgical Pathology Criteria

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Gastrointestinal Tract Perineurioma


  • Gastrointestinal tract mesenchymal neoplasm exhibiting features of perineurial cell differentiation

Alternate/Historical Terms

  • Fibroblastic polyp of the colon

Diagnostic Criteria

  • Circumscribed expansion of lamina propria
    • Usually limited by disrupted muscularis mucosae
    • Infrequent cases may extend into submucosa
    • May be separated from overlying surface mucosa by a narrow zone of normal lamina propria
    • Separates, entraps and distorts crypts
  • Composed of uniform, bland spindled cells
    • Oval to elongate nuclei
    • No pleomorphism, atypia or mitotic figures
  • Pale indistinct cytoplasm
  • Virtually restricted to left colon and rectum
    • Rarely in right colon or small intestine
  • Entrapped crypts frequently hyperplastic/serrated 50-70% of cases
  • Usually ≤10 mm
    • Rarely up to 4.5 cm
  • Positive for markers of perineurial cells (see Supplemental Studies)
  • Lesions reported as GI tract fibroblastic polyp appear to be the same lesion as perineurioma

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

Original posting/updates : 11/29/09, 10/26/10, 3/28/11, 11/11/11

Supplemental studies


EMA >90% faint, focal
Claudin I >90%
Glut1 100%
Collagen type IV 100%
CD34 15-30%
  • All four are markers of perineurial cells
  • EMA requires high concentration, prolonged incubation and/or special antigen retrieval to give even a weak reaction
    • Studies using normal EMA staining techniques and no other perineurial markers got negative results
      • These studies resulted in the diagnosis of fibroblastic polyp
      • It appears that fibroblastic polyp is identical to perineurioma in the GI tract
  • Negative markers: S100, GFAP, caldesmon, CD1117/CKIT, smooth muscle actin, desmin, keratin
  • Vimentin is strongly positive but nonspecific

Genetic study

  • BRAF or KRAS mutations characteristic of hyperplastic polyps were demonstrated in 2/3 of cases studied (Agaimy)
    • This suggests that GI perineuriomas are actually best considered mixed epithelial-stromal polyps

Differential Diagnosis

We consider Fibroblastic Polyp to be the same lesion as GI Perineurioma

Inflammatory Fibroid Polyp GI Perineurioma
Submucosal Predominantly lamina propria
Eosinophil rich inflammatory infiltrate Eosinophils and inflammation infrequent
Perivascular concentric cuffing common Lacks prominent concentric cuffing
Fibromyxoid background with regular vascular pattern Rarely may be myxoid but lacks regular vascular pattern
CD34 positive in 80% CD34 weak focal in 15-30%

GI Schwannoma GI Perineurioma
Peripheral lymphoid cuff common Lacks lymphoid cuff
Frequent cell size variation Generally uniform cell size
Most cases intramural Predominantly lamina propria
S100 100% S100 negative
GFAP 65-100% GFAP negative
Perineurial markers negative Perineurial markers positive

GI Ganglioneuroma GI Perineurioma
Ganglion cells present No ganglion cells
S100 100% S100 negative
Perineurial markers negative Perineurial markers positive

GI Neurofibroma GI Perineurioma
S100 positive S100 negative
Perineurial markers negative Perineurial markers positive
Axons present No axons in lesion

GI Mucosal Schwann Cell Hamartoma GI Perineurioma
Abundant cytoplasm Scant cytoplasm
No association with hyperplastic crypts Frequently associated with hyperplastic crypts
Perineurial markers negative Perineurial markers positive
S100 positive S100 negative

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


  • Mean age 50-60
    • Range 35-84
  • Most are incidental
  • No recurrences


  • Bosman FT, Carneiro F, Hruban RH, Thiese ND (Eds). WHO Classifiication of Tumors of the Digestive System, IARC, Lyon 2010.
  • Hornick JL, Fletcher CD. Intestinal perineuriomas: clinicopathologic definition of a new anatomic subset in a series of 10 cases. Am J Surg Pathol. 2005 Jul;29(7):859-65.
  • Zamecnik M, Chlumska A. Perineurioma versus fibroblastic polyp of the colon. Am J Surg Pathol. 2006 Oct;30(10):1337-9. No abstract available.
  • Eslami-Varzaneh F, Washington K, Robert ME, Kashgarian M, Goldblum JR, Jain D. Benign fibroblastic polyps of the colon: a histologic, immunohistochemical, and ultrastructural study. Am J Surg Pathol. 2004 Mar;28(3):374-8.
  • Groisman GM, Polak-Charcon S, Appelman HD. Fibroblastic polyp of the colon: clinicopathological analysis of 10 cases with emphasis on its common association with serrated crypts. Histopathology. 2006 Mar;48(4):431-7.
  • Groisman GM, Polak-Charcon S. Fibroblastic polyp of the colon and colonic perineurioma: 2 names for a single entity? Am J Surg Pathol. 2008 Jul;32(7):1088-94.
  • 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.
  • Pai RK, Mojtahed A, Rouse RV, Soetikno RM, Kaltenbach T, Ma L, Arber DA, Plesec TP, Goldblum JR, Pai RK. Histologic and molecular analyses of colonic perineurial-like proliferations in serrated polyps: perineurial-like stromal proliferations are seen in sessile serrated adenomas. Am J Surg Pathol. 2011 Sep;35(9):1373-80.
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