Neurofibroma
Epidemiology:
Common sites:
- skin
- peripheral nerve
- plexiform neurofibroma:
- large nerve
trunk most common
- anywhere along a
nerve
- irregular
expansion of nerve
Gross features:
- cutaneous neurofibroma
- nodule in the
dermis and subcutaneous fat
- well-delineated,
unencapsulated
- overlying hyperpigmentation sometimes
- may be pedunculated
- plexiform neurofibroma:
- multifocal often
- not possible to
separate from nerve
Histologic features:
- adnexal structures may be enwrapped by the
edges of the lesion
- collagenized stroma
with myxoid material
- plexiform neurofibroma:
- infiltrates
amongst fascicles of nerve
- fingers of tumour and individual cells between nerve fibres (extend proximal and distal to main lesion)
- loose, myxoid background; low cellularity
- multiple cell
types:
- schwann cells – elongated nuclei and
extensions of pink cytoplasm
- multipolar fibroblastic cells – larger
- inflammatory
cells – including mast cells often
- collagen bundles
with “shredded carrot” appearance
- axons can be
demonstrated within the tumour (contrast to schwannoma)
Immunophenotype:
Marker:
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Sensitivity:
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Specificity:
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Molecular features:
Other features:
- cutaneous and solitary neurofibromas
occur sporadically or in association with neurofibromatosis type 1
- plexiform neurofibromas
occur “only” in patients with neurofibromatosis type 1
- significant risk
of malignant transformation in plexiform neurofibroma only
References: