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Neural Tumours

Pathology of Neurofibroma     

Dr Sampurna Roy MD                   

Dermatopathology Quiz Case 183

Diagnosis : Neurofibroma




Solitary Neurofibroma:

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. 

(Differential diagnosis: 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.

There are thin and thick collagen strands (shredded carrot collagen).

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).


-Cutaneous Lipomatous Neurofibroma: 

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

Differential diagnosis:  Myxoid DFSP

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

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

-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:


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.

What is occult neurofibroma ? Occult neurofibroma and increased S100 protein in the skin of patients with neurofibromatosis type 1: new insight to the etiopathomechanism of neurofibromas.

Neurofibromatosis: For more information visit: Pathology of Neurofibromatosis

Neurofibromatosis was described by von Recklinhausen in 1882. 

Visit: Pathology Photo of the day - Stay CALM and have Coffee

Diffuse Neurofibroma

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:

Age: Usually occurs in children and young adults.

Site: Head and neck region

Clinical presentation: 

The expanded nerves form irregular, convoluted cords and nodules.  

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.



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


Differential diagnosis:  Plexiform Schwannoma


Further reading

Radiation induced peripheral nerve tumors: case series and review of the literature.

Cellular neurofibroma with atypia mimics sarcoma: report of a case with immunohistochemical staining pattern analysis and literature review.

Plexiform neurofibroma in type 1 neurofibromatosis.

Neurofibroma of the lingual nerve: a case report.

Vacuolated cells in neurofibroma: an immunohistochemical study.

Cutaneous lipomatous neurofibroma: characterization and frequency.

Cutaneous Lipomatous Neurofibroma.

Intratumoral fat in neurofibroma.

Benign Epithelioid Peripheral Nerve Sheath Tumors of the Soft Tissues: Clinicopathologic Spectrum of 33 Cases.




Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)






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