Peripheral nerve sheath tumor
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Peripheral nerve sheath tumours (PNST's(PNSTs) are are a group of primary neurogenic tumours that arise from nerve sheaths outside of the central nervous system. The vast majority are benign, however, malignant transformation is seen particularly in large tumours and those associated with neurofibromatosis type 1 (NF1).
Classification
Their imaging appearances, demographics, treatment and prognosis vary greatly and these are therefore discussed separately.
Pathology
They can be benign or malignant.
Classification
They matPeripheral nerve sheath tumours may be classified as follows:
- benign
-
schwannoma
(peripheral nerve sheath schwannoma) -
neurofibroma
(peripheral nerve sheath neurofibroma)-
localised neurofibroma
(~90%)- localised cutaneous neurofibroma
- localised intraneural neurofibroma
- diffuse cutaneous neurofibroma
-
plexiform neurofibroma
: arborising tumour of peripheral nerves that is pathognomonic of NF1
-
localised neurofibroma
- perineurioma
- hybrid nerve sheath tumour
-
schwannoma
- malignant
Associations
-
neurofibromatosis type 1(neurofibromas)
Radiographic features
Imaging of a solitary peripheral nerve sheath tumour, in most cases, cannot reliably distinguish between the different histological subtypes, and a presumptive diagnosis must take into account the patient demographics, including pre-existing conditions (such as neurofibromatosis type 1 or neurofibromatosis type 2), the location and size of the tumour, and evidence of rapid growth. As such these are discussed separately in each of the aforementioned tumours. A number of features are, however, shared by localised neurogenic tumours of peripheral nerves.
MRI
As a group they, localised peripheral nerve sheath tumours demonstrate the following features:
- fusiform-shaped mass with tapered ends
-
a “split-fat” sign -
atrophy, with nerve seen leading into and out of the mass - split-fat sign
- fascicular sign
- target sign
- denervation changes in muscles supplied by the involved nerve
-
a “fascicular sign” -
a “target sign”
-<p><strong>Peripheral nerve sheath tumours (PNST's)</strong> are a group of primary tumours that arise from nerve sheaths.</p><h4>Pathology</h4><p>They can be benign or malignant.</p><h5>Classification</h5><p>They mat be classified as follows</p><ul>- +<p><strong>Peripheral nerve sheath tumours (PNSTs)</strong> are a group of primary <a title="Neurogenic tumours" href="/articles/neurogenic-tumours-1">neurogenic tumours</a> that arise from nerve sheaths outside of the central nervous system. The vast majority are benign, however, malignant transformation is seen particularly in large tumours and those associated with <a title="Neurofibromatosis type 1 (NF1)" href="/articles/neurofibromatosis-type-1">neurofibromatosis type 1 (NF1)</a>. </p><h4>Classification</h4><p>Their imaging appearances, demographics, treatment and prognosis vary greatly and these are therefore discussed separately.</p><p>Peripheral nerve sheath tumours may be classified as follows:</p><ul>
- +<li><a title="Schwannoma" href="/articles/schwannoma">schwannoma</a></li>
-<a href="/articles/schwannoma">schwannoma</a> (<a href="/articles/peripheral-nerve-sheath-schwannoma">peripheral nerve sheath schwannoma</a>)</li>-<li>-<a href="/articles/neurofibroma">neurofibroma</a> (<a href="/articles/peripheral-nerve-sheath-neurofibroma">peripheral nerve sheath neurofibroma</a>)<ul>-<li>-<a href="/articles/localised-neurofibroma">localised neurofibroma</a> (~90%)</li>-<li><a href="/articles/missing">diffuse neurofibroma</a></li>-<li>-<a href="/articles/plexiform-neurofibroma">plexiform neurofibroma</a>: arborising tumour of peripheral nerves that is pathognomonic of NF1</li>- +<a title="Neurofibroma" href="/articles/neurofibroma">neurofibroma</a><ul>
- +<li>localised neurofibroma<ul>
- +<li>localised cutaneous neurofibroma</li>
- +<li>localised intraneural neurofibroma</li>
- +<li><a title="Diffuse cutaneous neurofibroma" href="/articles/diffuse-cutaneous-neurofibroma">diffuse cutaneous neurofibroma</a></li>
- +<li><a title="Plexiform neurofibroma" href="/articles/plexiform-neurofibroma">plexiform neurofibroma</a></li>
-<li>malignant<ul><li>-<a href="/articles/malignant-peripheral-nerve-sheath-tumour">malignant peripheral nerve sheath tumour</a> (MPSNT)</li></ul>- +<li><a title="Perineurioma" href="/articles/perineurioma">perineurioma</a></li>
- +<li><a title="Hybrid nerve sheath tumour" href="/articles/hybrid-nerve-sheath-tumour">hybrid nerve sheath tumour</a></li>
- +</ul>
- +</li>
- +<li>malignant<ul><li><a title="Malignant peripheral nerve sheath tumour" href="/articles/malignant-peripheral-nerve-sheath-tumour">malignant peripheral nerve sheath tumour</a></li></ul>
-</ul><h5>Associations</h5><ul><li>-<a href="/articles/neurofibromatosis-type-1">neurofibromatosis type 1</a> (neurofibromas)</li></ul><h4>Radiographic features</h4><p>Imaging, in most cases, cannot reliably distinguish between these tumours.</p><h5>MRI</h5><p>As a group they demonstrate the following features</p><ul>-<li>fusiform-shaped mass with tapered ends</li>-<li>a “<a href="/articles/split-fat-sign">split-fat</a>” sign</li>-<li>atrophy of the muscles supplied by the involved nerve</li>-<li>a “<a href="/articles/fascicular-sign">fascicular sign</a>”</li>-<li>a “<a href="/articles/target-sign-of-neurofibromas">target sign</a>”</li>- +</ul><h4>Radiographic features</h4><p>Imaging of a solitary peripheral nerve sheath tumour, in most cases, cannot reliably distinguish between the different histological subtypes, and a presumptive diagnosis must take into account the patient demographics, including pre-existing conditions (such as <a title="Neurofibromatosis type 1" href="/articles/neurofibromatosis-type-1">neurofibromatosis type 1</a> or <a title="Neurofibromatosis type 2" href="/articles/neurofibromatosis-type-2-3">neurofibromatosis type 2</a>), the location and size of the tumour, and evidence of rapid growth. As such these are discussed separately in each of the aforementioned tumours. A number of features are, however, shared by localised neurogenic tumours of peripheral nerves. </p><h5>MRI</h5><p>As a group, localised peripheral nerve sheath tumours demonstrate the following features:</p><ul>
- +<li>fusiform-shaped mass with tapered ends, with nerve seen leading into and out of the mass</li>
- +<li><a title="Split fat sign" href="/articles/split-fat-sign">split-fat sign</a></li>
- +<li><a title="Fascicular sign" href="/articles/fascicular-sign">fascicular sign</a></li>
- +<li><a title="Target sign (neurofibromas)" href="/articles/target-sign-neurofibromas">target sign</a></li>
- +<li>
- +<a title="Denervation changes in muscles" href="/articles/denervation-changes-in-muscles">denervation changes in muscles</a> supplied by the involved nerve</li>
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