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NEURILEMMOMA (SCHWANNOMA)

Introduction

Schwannomas, also called neurilemmomas, are peripheral nerve sheath tumors composed entirely of benign neoplastic Schwann cells. They are the most common tumor of peripheral nerves, and with exception of rare variants, they do no transform to malignant lesions.

Pathophysiology

  • The schwannoma is a benign proliferation of Schwann cell origin
  • Solitary tumors range in size from 1.5–3 cm in diameter
  • Tumors are well-circumscribed masses exhibiting Antoni A (stacked or storiform) and Antoni B (disorganized or myxoid) pattern, nuclear palisading (Verocay bodies) and a fibrous capsule
  • Schwannoma variants include:
    • Cellular schwannoma (uncommon but important because although benign, its alarming cellularity often prompts consideration of malignancy)
    • Plexiform schwannoma (difficult to distinguish from Malignant Peripheral Nerve Sheath Tumor [MPNST] when observed in a deep anatomic location)
    • Melanotic schwannoma (potentially malignant; characterized by marked accumulation of melanin)

Related Anatomy

  • Usually eccentrically located relative to the cross sectional view of the nerve and encapsulated

Incidence and Related Conditions

  • Schwannoma is the most common tumor of peripheral nerves
  • Schwannomas usually occur between the ages of 30–50 years
  • There are no racial or gender differences in epidemiology
  • Schwannomas located in the upper extremity account for 12–19% of all cases
  • Schwannomas are mostly located on volar surface of the upper extremity.
  • Schwannomas are also seen as part of neurofibromatosis 2 (NF2), schwannomatosis and Carney complex
  • Schwannomas do not occur in neurofibromatosis type 1 (NF1)

Differential Diagnosis

  • Neurofibroma
  • MPNST (differential diagnosis with cellular schwannoma, plexiform schwannoma)
  • Leiomyosarcoma (differential diagnosis with cellular schwannoma)
  • Gastrointestinal stromal tumor (differential diagnosis with cellular schwannoma)
  • Melanoma (differential diagnosis with melanotic schwannoma)
ICD-10 Codes

  • NEUROLIMMOMA (SCHWANNOMA)

    Diagnostic Guide Name

    NEUROLIMMOMA (SCHWANNOMA)

    ICD 10 Diagnosis, Single Code, Left Code, Right Code and Bilateral Code

    DIAGNOSISSINGLE CODE ONLYLEFTRIGHTBILATERAL (If Available)
    NEUROLIMMOMA (SCHWANNOMA), BENIGND36.12   

    ICD-10 Reference

    Reproduced from the International statistical classification of diseases and related health problems, 10th revision, Fifth edition, 2016. Geneva, World Health Organization, 2016 https://apps.who.int/iris/handle/10665/246208

Clinical Presentation Photos and Related Diagrams
Schwannoma Clinical Cases
  • Schwannoma (arrow) Dorsal Ulnar Sensory Nerve
    Schwannoma (arrow) Dorsal Ulnar Sensory Nerve
Basic Science Photos and Related Diagrams
Schwannoma Diagram
Basic Science Pics
  • Schwannoma (1) has well defined borders and is eccentrically located in the nerve between the fascicular groups. There is a thin layer of epineurium over the tumor (2). The external epineurium (3) is visible on the cut end. The cross section shows the fascicular groups (4) surrounded by normal internal epineurium.
    Schwannoma (1) has well defined borders and is eccentrically located in the nerve between the fascicular groups. There is a thin layer of epineurium over the tumor (2). The external epineurium (3) is visible on the cut end. The cross section shows the fascicular groups (4) surrounded by normal internal epineurium.
Symptoms
Dysesthesia can occur
Painful mass
Asymptomatic mass
Typical History

There is no specific presentation unique to schwannoma.  Patients may present for evaluation because of a soft tissue mass, pain or focal neurologic findings. Patients may complain of a tingling sensation when the mass is bumped.  By definition, schwannomas do not intertwine with nerve fascicles (unlike neurofibromas) and therefore, the nerve may be spared with surgical excision. Recurrence of schwannomas is rare.   

Positive Tests, Exams or Signs
Work-up Options
Treatment Options
Treatment Goals
  • Remove the tumor
  • Preserve nerve function
  • Stop or decrease pain
Conservative
  • Observation - the need to control symptoms and to establish a tissue diagnosis makes this a difficult recommendation.
Treatment Photos and Diagrams
  • Schwannoma - Note tiny intact nerve fibers at tip of arrow.
    Schwannoma - Note tiny intact nerve fibers at tip of arrow.
  • Schwannoma - Note preserved nerve fibers
    Schwannoma - Note preserved nerve fibers
  • Excised Neurilemmoma (Schwannoma)
    Excised Neurilemmoma (Schwannoma)
  • Case 2 - Schwannoma radial digital nerve of the index finger
    Case 2 - Schwannoma radial digital nerve of the index finger
  • Case 2 - Schwannoma radial digital nerve of the index finger.
    Case 2 - Schwannoma radial digital nerve of the index finger.
  • Case 2 - Schwannoma radial digital nerve of the index finger. Schwannoma removed (in forceps). Note radial digital nerve intact but a hole remains between the fascicular groups.
    Case 2 - Schwannoma radial digital nerve of the index finger. Schwannoma removed (in forceps). Note radial digital nerve intact but a hole remains between the fascicular groups.
CPT Codes for Treatment Options

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Common Procedure Name
Excision benign nerve tumor
CPT Description
Excision of neurofibroma or neurolemmoma; cutaneous nerve
CPT Code Number
64788
CPT Code References

The American Medical Association (AMA) and Hand Surgery Resource, LLC have entered into a royalty free agreement which allows Hand Surgery Resource to provide our users with 75 commonly used hand surgery related CPT Codes for educational promises. For procedures associated with this Diagnostic Guide the CPT Codes are provided above. Reference materials for these codes is provided below. If the CPT Codes for the for the procedures associated with this Diagnostic Guide are not listed, then Hand Surgery Resource recommends using the references below to identify the proper CPT Codes.

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CPT 2021 Professional Edition: Spiralbound

Complications
  • Recurrence after excision (very rare)
  • Loss of nerve sensation distal to the lesion
  • Persistent pain after tumor excision
Outcomes
  • Temporary sensory and/or motor dysfunction might occur after surgical excision, but long-term sensory or functional deficits seldom occur.
  • Recurrence after surgical excision is rare.
Key Educational Points
  • Schwannomas show a diffuse contrast enhancement on a T1-weighted MRI and a hypodense mass compared to muscle on CT
  • The immunohistochemical markers S100 and Sox10 have over 90% specificity for tumors of neural crest origin (schwannomas).3
  • Pericellular collagen type IV occurs in schwannomas
References

New Articles

  1. Gosk J, Gutkowska O, Urban M, et al. Results of surgical treatment of schwannomas arising from extremities. Biomed Res Int 2015;2015:547926. PMID: 25793198
  2. Tang C, Fung B, Fok M, et al. Schwannoma in the upper limbs. Biomed Res Int 2013;2013:167196. PMID: 24093090
  3. Karamchandani JR, Nielsen TO, van de Rijin M, West RB.  Sox10 and S100 in the diagnosis of soft tissue neoplasms. Appl Immunohistochem Moi Morphol 2012 Oct; 5:445-450.

Reviews

  1. Rodriguez F, Folpe A, Giannini C, et al. Pathology of peripheral nerve sheath tumors: diagnostic overview and update on selected diagnostic problems. Acta Neuropathol 2012;123(3):295-319. PMID: 22327363
  2. Clarke S, Kaufmann R. Nerve tumors. J Hand Surg Am 2010;35(9):1520-2. PMID: 20807630
  3. Skovronsky D, Oberholtzer J. Pathologic classification of peripheral nerve tumors. Neurosurg Clin N Am 2004;15(2):157-66. PMID: 15177315

Classics

  1. Strickland J, Steichen J. Nerve tumors of the hand and forearm. J Hand Surg Am 1977;2(4):285-91. PMID: 197148
  2. Verocay J. Multiple tumors as a systemic disease of the nervous system. In: Memorial Publication, dedicated to Hans Chiari on occasion of his 25th year professorship jubilee. Vienna, Leipzig: W. Braunmueller; 1908:378-415.
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