SOLITARY NEUROFIBROMA: IMAGE LINKS1  2  3  4 (ESCOP)

Solitary neurofibroma is a localized neurofibroma which is usually not associated with  neurofibromatosis.

Age: This lesion usually occurs between the ages of 20 and 30.

Clinical presentation: Solitary neurofibromas are papular, nodular or pedunculated lesions and greyish white in colour. These painless , slow growing tumours  are soft in consistency.  Usually there is no evidence of secondary degenerative changes.  (D/D: Schwannoma).               
The tumour appears to originate within the endoneurium.

Microscopic features: 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 fibromyxoid backround. Mast cells are present.  Sometimes degenerative 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).

Variants:

-Cutaneous Lipomatous Neurofibroma: Read abstracts

-Myxoid neurofibroma - Myxoid Tumours of Soft Tissue: Abundant mucin is present in the matrix  (S100 necessary to distinguish from intramuscular myxoma.)  D/D:  Myxoid DFSP

-Collagenous neurofibroma - Thick collagen bundles are present in the matrix.

-Epithelioid neurofibroma - The tumour cells are rounded with eosinophilic cytoplasm. Read abstract

-Granular neurofibroma - The cells contain granular PAS positive, diastase resistant cytoplasm.

-Pigmented neurofibroma - Scattered tumour cells contain melanin pigment (S100 protein, HMB45 and Melan A positive).

-Dendritic Cell Neurofibroma With Pseudorosettes:Read abstract

                                                     
Immunohistochemistry: 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. Factor XIIa positive and CD34 positive cells are also sometimes present.

NEUROFIBROMATOSIS:

Neurofibromatosis was 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 patients.
There may be skeletal abnormalities (kyphoscoliosis, bone hypertrophy, pseudoarthrosis).
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. Cutaneous 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.

N-7: Late onset type. 

N-8:  Miscellaneous group
                                                                       

DIFFUSE  NEUROFIBROMA:

 IMAGE LINKS 1  2  3  4  5 (ESCOP)

Age:  Occurs between ages of 10-30 years.

Site:  Head and neck area.

Clinical presentation:  Plaque like elevation of the skin. On cut section, entire subcutis is thickened by firm greyish tissue.

Microscopic features :  Poorly  defined lesion with diffuse replacement of the dermis and subcutis by neurofibromatous tissue. It diffusely infiltrate subcutaneous fat.  It does not destroy but envelops the normal structure. The matrix of the lesion is uniform consisting of fine fibrillary collagen. The Schwann cells have shorter and more  rounded contour in diffuse neurofibroma. Clusters of Meissner bodies may be present. Occasionally multinucleate giant cells may be present.

Differential diagnosis:
Dermatofibrosarcoma protruberance - More storiform pattern and CD34 positive and S100 protein negative.

PLEXIFORM  NEUROFIBROMA:

IMAGE LINK (Dr. Weems)
IMAGE LINKS1  2  3  4 (ESCOP)     

Age: Usually occurs in children and young adults.

Site: Head and neck region

Clinical presentation:  The expanded nerves form irregular, convoluted cords and nodules.  

GROSS: CLICK HERE(DermAtlas)

Plexiform neurofibroma is associated with hyperpigmented skin, thickening of soft tissue and hypertrophy of bone.

Microscopic features:  Nodules of tortuous, expanded nerve branches cut in various planes of section.
There is prominent myxoid change. In some cases cells spill out from the nerve into the soft tissue.
In early stage, the affected nerve displays  increase in endoneurial matrix. 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.

Immunohistochemistry:  Axon- Neurofilament positive
Schwann cells- S100 protein positive
Perineurial cells- EMA positive

D/D:  Plexiform Schwannoma

 MORE IMAGE LINKS (Dr Weems):  1   2   3