This document summarizes benign and malignant nerve sheath tumors. It describes neurofibroma as a common benign peripheral nerve tumor that can be solitary or associated with neurofibromatosis. Schwannoma is another benign nerve sheath tumor that arises from Schwann cells. Malignant peripheral nerve sheath tumor is described as a rare malignant schwannoma that commonly affects young adults and is associated with rapid growth and nerve deficits. The document provides details on clinical features, histopathology, treatment and prognosis of these nerve sheath tumors.

1. BENIGN AND MALIGNANT NERVE
SHEATH TUMORS
DR.PRIYADHARSINI N
DEPARTMENT OF ORAL PATHOLOGY AND MICROBIOLOGY
SRM DENTAL COLLEGE , RAMAPURAM

2. Neurofibroma
 Common type of peripheral nerve neoplasm
 Arise from mixture of cells including perineural fibroblasts

3.  Can arise as solitary tumor or
neurofibromatosis
 Common in young adults
 Slow growing, soft painless lesion
varying in size from small nodule to
large masses

4.  Skin is the most common location
 Tongue and buccal mucosa common
in oral cavity
 Rarely arise within bone producing
well demarcated or poorly define
unilocular or multilocular
radiolucency.

5. Histopathology
 Well circumscribed within perineurium
 When occurs outside tend to blend
with adjacent connective tissues
 Composed of interlacing bundles of
spindle shaped cells exhibiting wavy
nuclei.

6.  Associated with delicate collagen and
variable myxoid matrix.
 Mast cells are numerous and are
diagnostic
 Sparsely distributed small axons
demonstrable by silver stains.
 IHC – S100 positive

7. Treatment
 Local surgical excision
 Recurrence is rare
 Should be evaluated for neurofibromatosis
 Malignant transformation possible.

8. Neurofibromatosis
 Common hereditary condition
 Eight forms have been recognized.
 Type I – von Recklinghausen disease
 Autosomal dominant trait
 Caused by NF1 gene mutation
responsible for tumor suppressor
protein neurofibromin

9. Clinical features
 Multiple neurofibromas that can occur
anywhere in body
 Clinical appearance can vary from
small papule to large soft nodules to
massive baggy pendulous masses
(elephantiasis neuromatosa) on skin

10.  Plexiform variant feels like a bag of
worms and considered
pathognomonic
 May be present at birth but appear
during puberty
 Accelerated growth seen in pregnancy

11.  Café au lait (coffee with milk )
pigmentation on skin
 Occur as yellow – tan to dark brown
macules that vary in diameter from 1 –
2 mm to several centimeters.
 They have a smooth edge “coast of
California”
 Coast of maine – Polyostotic fibrous
dysplasia

13.  Crowe sign – freckling of axilla

14.  Lisch nodules – translucent brown
pigmented spots on iris
 Hypertension, CNS tumors, short
stature, scoliosis, mental deficiency
are other complications

15. Oral manifestation
 Enlargement of fungiform papilla
 Only very few patient develop
intraoral neurofibromas
 Radiograph shows enlargement of
mandibular canal, increased bone
density, concavity of medial surface of
ramus

16.  The 7 clinical criteria used to diagnose NF1 are as follows: (the patient
should have two or more of following)
• Six or more café-au-lait spots or hyperpigmented macules greater than 5
mm in diameter in prepubertal children and greater than 15 mm
postpubertal
• Axillary or inguinal freckles (>2)
• Two or more typical neurofibromas or one plexiform neurofibroma
• Optic nerve glioma
• Two or more iris hamartomas (Lisch nodules), often identified only through
slit-lamp examination by an ophthalmologist
• Sphenoid dysplasia or typical long-bone abnormalities such as
pseudarthrosis
• First-degree relative (eg, mother, father, sister, brother) with NF1

17. Treatment
 Prevention and management of complications
 Facial neurofibromas can be removed using carbon di oxide laser and
dermabrasion
 Some may require cosmetic remodeling surgery
 Complication – neurofibrosarcoma , MPNST

18. Shwannoma (Neurilemoma)
 Schwannoma is a benign neural neoplasm of Schwann cell origin.
Relatively uncommon
 Schwannomatosis – multiple schwannomas
 Neurofibromatosis II – Bilateral schwannomas of auditory vestibular nerve

19. Clinical features
 Slow growing, encapsulated tumor arising in association with nerve trunk
 It pushes the nerve aside as it grows.
 Asymptomatic, tender in some instances
 Common in young and middle aged adults
 Range from a few millimeters to several centimeters in size

20.  Tongue is the most common location
 Occasionally arise within bone
 Pain and paresthesia present in intrabony tumors

21.  NF2 – caused my mutation of tumor suppressor gene NF2 which codes for
protein merlin
 Schwannomatosis related to mutation of SMARCB1 gene.

22. Histopathology
 Encapsulated tumor demonstrating
two microscopic patterns in varying
amounts
 Antoni A and Antoni B
 Streaming fascicles of spindle shaped
Schwann cells – Antoni A
 Form palisaded arrangement around
central acellular, eosinophilc areas
known as Verocay bodies.

23.  Verocay bodies contain reduplicated
basement membrane and cytoplasmic
processes.
 Antoni B – less cellular and less
organized and spindle cells randomy
arranged within loose, myxomatous
storma

24.  Degenerative changes seen in older tumors containing hemorrhage,
hemosiderin deposits, inflammation, fibrosis and nuclear atypia.
 Plexiform schwannoma another variant – multinodular plexiform growth
pattern. May be associated with NF2 or Shwannomatosis

25. Treatment
 Treated by surgical excision
 Malignant transformation is very rare

26. Malignant peripheral nerve sheath
tumor
 Malignant schwannoma, neurofibrosarcoma, neurogenic sarcoma
 Malignancy of peripheral nerve origin
 Common in proximal portion of extremities and trunk

27. Clinical and radiographic features
 Common in young adults.
 Mean age 29-36 years
 Enlarging mass that exhibits rapid growth.
 Associated pain or nerve deficit is common
 Oral tumors may occur anywhere
 Most common sites are mandible, lips and buccal mucosa
 Radiographic examination of intraosseous tumors reveal widening of
mandibular canal or mental foramen with or without irregular destruction
of surrounding bone

28. Histopathologic features
 Fascicles of atypical spindle shaped
cells resembling fibrosarcoma
 More irregular in shape with wavy or
comma shaped nuclei.
 Less cellular myxoid areas also may be
present.
 With some tumors heterologous
elements including skeletal muscle
differentiation (triton tumor),
cartilage, bone or glandular structures

29. Treatment
 Radical surgical excision along with radiation and chemotherapy.
 Prognosis is generally poor especially in patients with neurofibromatosis
type I