Malignant
Peripheral Nerve Sheath Tumour (MPNST)
Epidemiology:
Common sites:
- anwhere
- peripheral
extremities most common in solitary form
- skin
- head and neck
- retroperitoneum
- Neurofibromatosis
1:
- Central in the
trunk or head and neck mostly
Gross features:
- poorly-defined
- frequent
infiltration along parent nerve
- necrosis common
Histologic features:
- heterologous / wide range of patterns
- similar to fibrosarcoma or MFH
- fascicles
intersecting at acute angles (herringbone)
- fascicle
formation
- alternating hypocellular and hypercellular
regions
- nuclear palisading (may also be prominent in leiomyosarcoma)
- nerve-like
whorls or tactoid bodies resembling Wagner-Meissner corpuscles
- schwann cells may be present
- elongated, thin,
wavy, comma-shaped, or bullet-shaped nuclei
- prominent
bipolar processes
- nuclear pleomorphism can be extreme
- prominent,
thick-walled vasculature
- densely cellular
areas can indicate malignancy in a nerve sheath tumour
- mitoses common
- even 1 per 20HPF
can be evidence of potentially malignant behaviour
- necrosis common
- extreme nuclear atypia common
- purely epithelioid
type (5%)
- nodular pattern
- necrosis
virtually always
- closely packed epithelioid cells in sheets
- small foci of
spindling and more classic nerve sheath morphology in areas of hypocellularity
- nuclei rounded
with evenly dispersed chromatin
- may have
prominent nucleoli
- CK neg, S100 pos
Immunophenotype:
|
Marker:
|
Sensitivity:
|
Specificity:
|
|
S100 (focal)
|
50-75%
|
|
|
CD57 (Leu-7) (focal)
|
50%
|
|
Molecular features:
Other features:
- highly aggressive
- may arise de novo
or from plexiform neurofibroma
or post-radiation
- rare to develop
from precursor lesion in sporadic cases
- associated with
neurofibromatosis type 1
- may develop from
longstanding neurofibromas
- occasionally
painful
References:
- Robbins 2005
- Sternberg 2004