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Gastrointestinal Tract Schwannoma

Definition

  • Gastrointestinal tract mesenchymal neoplasm exhibiting features of Schwann cell differentiation

Diagnostic Criteria

  • Circumscribed, non-encapsulated nodule centered in muscularis propria
    • Microscopically entraps adjacent muscle fibers
    • Occasional lesions are lobular
    • Benign intramucosal Schwann cell proliferations are a different lesion(s)
  • S100 positive
  • Predominantly bland spindled cells
    • Scattered cells with large hyperchromatic nuclei present in nearly all cases
    • Mitotic figures <5/50 HPF
    • PAS/d+ crystalloids described in some cases
  • Nearly all have surrounding lymphoid cuff
    • Predominantly B cells
    • Frequently contains germinal centers
    • Smaller number of lymphocytes scattered throughout
  • Most common pattern is trabecular
    • Bundles of spindle cells alternating with fibrovascular trabeculae
    • Occasional sheets and storiform pattern
    • Vague palisading at most
    • May be myxoid
    • May have cystic degeneration
    • No necrosis
  • Epithelioid patterns have been reported
    • From focal to complete
    • Most lack lymphoid cuff
    • May form pseudoglandular spaces or microcystic spaces
    • One reported with metaplastic bone
    • Epithelioid lesions confined to the lamina propria are classified separately
  • >90% in stomach, mostly antrum
    • Rarely reported in colorectum and esophagus
  • GI schwannoma differs significantly from soft tissue schwannoma and may be a separate lesion
  • GI Schwannoma Soft Tissue Schwannoma
    Prominent lymphoid cuff No lymphoid cuff
    Non-encapsulated Encapsulated
    Vague palisading at most Prominent palisading and Verocay bodies
    Lacks hyalinized vessels Frequent hyalinized vessels
    Lacks xanthoma cells Frequent xanthoma cells
    No NF2 mutations 40-60% have NF2 mutations
  • Rare cases of plexiform schwannoma reported(Sarlomo-Rikala 1995)
    • Multiple nodules, transmural
    • Palisaded with prominent Verocay bodies
    • No lymphoid cuff
    • Hyalinized vessels
    • This may represent a soft tissue type schwannoma
  • It is not clear if the 5 reported cases of GI microcystic/reticular schwannoma (Liegl 2008)are part of this spectrum
    • All lacked peripheral lymphoid cuffs, atypia or mitotic figures >5/HPF
    • One had a component of typical GI schwannoma
    • One was intramucosal and could perhaps be classified with benign epithelioid intramucosal nerve sheath tumors
    • Regardless of classification, the critical points for microcystic tumors are:
      • Pseudoglandular structures may simulate carcinoma
        • Keratin and S100 resolve this question
      • No association with NF1 or other syndromes

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

Original posting : November 29, 2009

Supplemental studies

Immunohistology

S100 100%
GFAP 64-100%
Nestin 79-96%
Collagen type IV 100%
p75 100%
CD34 0-33%
CD117, actin, desmin, neurofilaments, HMB45, myelin basic protein negative
p75 = low affinity nerve growth factor receptor

Differential Diagnosis

GI Schwannoma GIST (spindled, bland)
Peripheral lymphoid cuff common Lacks lymphoid cuff
Frequent cell size variation Generally uniform cell size
No skeinoid fibers May have skeinoid fibers
S100 100% S100 5% (20% in small intestine)
GFAP 65-100% GFAP negative
CD117 negative CD117 74-95%
Palisading is more accentuated in GIST; CD34 stains 0-33% of GI schwannomas

Inflammatory Fibroid Polyp GI Schwannoma
Eosinophil rich inflammatory infiltrate throughout Peripheral lymphoid cuff common
Perivascular concentric cuffing common, palisading rare May palisade, no concentric pattern
Fibromyxoid background with regular vascular pattern May be myxoid but lacks regular vascular pattern
S100 negative S100 100%

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 Schwannoma GI Ganglioneuroma
No ganglion cells Contains ganglion cells
Most cases intramural Predominantly lamina propria
Peripheral lymphoid cuff common Lacks lymphoid cuff

GI Schwannoma GI Neurofibroma
Most cases intramural Predominantly lamina propria
No association with neurofibromatosis Frequently associated with neurofibromatosis
Peripheral lymphoid cuff common Lacks lymphoid cuff

GI Schwannoma GI Mucosal Benign Epithelioid Nerve Sheath Tumor
Most cases intramural Most cases confined to lamina propria
Peripheral lymphoid cuff common Lacks lymphoid cuff
Frequent pleomorphic hyperchromatic cells No pleomorphism
Spindled cells Epithelioid cells

Clinical

  • Mean age 50-60
    • Range 18-87
  • Most are incidental
  • No association with neurofibromatosis
  • No recurrences or metastases

Bibliography

  • Daimaru Y, Kido H, Hashimoto H, Enjoji M. Benign schwannoma of the gastrointestinal tract: a clinicopathologic and immunohistochemical study. Hum Pathol. 1988 Mar;19(3):257-64.
  • Prévot S, Bienvenu L, Vaillant JC, de Saint-Maur PP. Benign schwannoma of the digestive tract: a clinicopathologic and immunohistochemical study of five cases, including a case of esophageal tumor. Am J Surg Pathol. 1999 Apr;23(4):431-6.
  • Hou YY, Tan YS, Xu JF, Wang XN, Lu SH, Ji Y, Wang J, Zhu XZ. Schwannoma of the gastrointestinal tract: a clinicopathological, immunohistochemical and ultrastructural study of 33 cases. Histopathology. 2006 Apr;48(5):536-45.
  • Miettinen M, Shekitka KM, Sobin LH. Schwannomas in the colon and rectum: a clinicopathologic and immunohistochemical study of 20 cases. Am J Surg Pathol. 2001 Jul;25(7):846-55.
  • Sarlomo-Rikala M, Miettinen M. Gastric schwannoma - a clinicopathological analysis of six cases. Histopathology 1995 Oct, 27(4): 355-60
  • Liegl B, Bennett MW, Fletcher CD. Microcystic/reticular schwannoma: a distinct variant with predilection for visceral locations. Am J Surg Pathol. 2008 Jul;32(7):1080-7.
  • Sarlomo-Rikala M, Tsujimura T, Lendahl U, Miettinen M. Patterns of nestin and other intermediate filament expression distinguish between gastrointestinal stromal tumors, leiomyomas and schwannomas. APMIS. 2002 Jun;110(6):499-507.
  • Lasota J, Wasag B, Dansonka-Mieszkowska A, Karcz D, Millward CL, Rys J, Stachura J, Sobin LH, Miettinen M. Evaluation of NF2 and NF1 tumor suppressor genes in distinctive gastrointestinal nerve sheath tumors traditionally diagnosed as benign schwannomas: s study of 20 cases. Lab Invest. 2003 Sep;83(9):1361-71
  • Yagihashi N, Kaimori M, Katayama Y, Yagihashi S. Crystalloid formation in gastrointestinal schwannoma. Hum Pathol. 1997 Mar;28(3):304-8.
  • Kwon MS, Lee SS, Ahn GH. Schwannomas of the gastrointestinal tract: clinicopathological features of 12 cases including a case of esophageal tumor compared with those of gastrointestinal stromal tumors and leiomyomas of the gastrointestinal tract. Pathol Res Pract. 2002;198(9):605-13.
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