Solitary neurofibroma is a
localized neurofibroma which is usually not associated with
This lesion usually occurs between the ages of 20 and 30.
Solitary neurofibromas are papular, nodular or pedunculated lesions and
greyish white in colour.
These painless, slow growing tumours are soft
Usually there is no evidence of secondary degenerative
(Differential diagnosis: Schwannoma).
The tumour appears to originate within the endoneurium.
The lesion is
nonencapsulated ( schwannoma is well encapsulated) and circumscribed.
A grenz zone separates the lesion from the epidermis.
The tumour is
composed of interlacing bundles of elongated cells with wavy nuclei.
Several small nerve fibres are also present.
The tumour cells are set in a
Mast cells are present.
nuclear pleomorphism may be present (bizarre or atypical neurofibroma).
Note: Presence of mitotic activity in neurofibroma is indicative of
malignancy. (Mitosis is common in schwannoma).
-Myxoid neurofibroma - Myxoid Tumours of Soft Tissue:
Abundant mucin is
present in the matrix (S100 necessary to distinguish from
collagen bundles are present in the matrix.
tumour cells are rounded with eosinophilic cytoplasm.
The cells contain
granular PAS positive, diastase resistant cytoplasm.
neurofibroma - Scattered tumour cells
contain melanin pigment (S100 protein, HMB45 and Melan A positive).
Neurofibroma With Pseudorosettes:
There is proliferation of all the elements of the peripheral nerve -
Schwann cells, axons , perineural cells (plexiform type) and fibroblasts.
Hence 30- 40% tumour cells are positive to S100 protein (in neurilemmoma
100% cells are positive).
Axons are neurofilament positive.
positive and CD34 positive cells are also sometimes present.
described by von Recklinhausen in 1882.
Neurofibromas may arise in any
part of the body including axilla, thigh, buttock, deep lying soft tissue,
orbit, mediastinum, retroperitoneum, tongue, gastrointestinal tract.
There are 8 clinical subtypes:
NF-1: Classic von Recklinghausen's disease is inherited as an autosomal
dominant trait. The responsible gene (NF1) is located in chromosome 17.
Plexiform neurofibroma is pathognomonic of NF-1.
Cafe-au-lait pigmentation (macular pigmentation) develops within the first
few years of life.
Multiple neurofibromas appear during childhood and adolescence after the
cafe au lait spots.
Pigmented hamartoma of the iris (Lisch nodules) are present in 90% of
There may be skeletal abnormalities (kyphoscoliosis, bone hypertrophy,
Malignant transformation may occur rarely.
NF-2: Central neurofibromatosis- Autosomal dominant disorder (alteration
of a gene located in chromosome 22). Associated with acoustic neuroma and a range of neoplasms of the central nervous system.
schwannomas may also be present.
NF-3: Characterized by combined features of NF-1 and NF-2.
NF-4: Characterized by diffuse neurofibroma and cafe-au-lait pigmentation.
Other features of NF-1are not present.
NF-5: Segmental form of neurofibromatosis where the disease is restricted
to one area of the body.
NF-6: Cafe-au-lait pigmentation is the only manifestation.
NF-7: Late onset
NF-8: Miscellaneous group
Occurs between ages of
Head and neck area.
Plaque like elevation
of the skin. On cut section, entire subcutis is thickened by firm greyish
Microscopic features :
lesion with diffuse replacement of the dermis and subcutis by
It diffusely infiltrate subcutaneous fat.
does not destroy but envelops the normal structure.
The matrix of the
lesion is uniform consisting of fine fibrillary collagen.
cells have shorter and more rounded contour in diffuse neurofibroma.
Clusters of Meissner bodies may be present.
giant cells may be present.
protruberance - More storiform pattern and CD34 positive and S100 protein negative.
Usually occurs in children and young adults.
Head and neck region
The expanded nerves form irregular, convoluted cords and nodules.
Plexiform neurofibroma is associated with hyperpigmented skin, thickening
of soft tissue and hypertrophy of bone.
Nodules of tortuous, expanded nerve branches cut in various planes of
There is prominent
In some cases cells spill out from the nerve into the soft
In early stage, the affected nerve displays increase in endoneurial
In the late stage the nerve fibres are replaced by proliferation
of Schwann cells together with thick wavy collagen bundles.
Presence of mitotic figures is indicative of malignancy.
Axon- Neurofilament positive
Schwann cells- S100 protein positive
Perineurial cells- EMA positive