4. Neurilemoma
The neurilemoma, sometimes referred to as a benign schwannoma,
is a nerve sheath tumor arising from the schwann cell surrounding
the axons of peripheral nerves. It affects individuals between the
ages of 20 and 50 years and occurs equally in males and females. It
is seen most commonly in spinal roots and superficial nerves,
especially on the flexor surface of both the upper and lower limbs.
The lesions are usually solitary but in the case of neurofibromatosis
multiple lesions may occur. These benign lesions are slow growing
and very rarely cause neurological symptoms or defect because
of their benign behavior. As opposed to the more common neuro-
fibroma, the neurilemoma is typically a round structure attached to
the periphery of a nerve whereas the neurofibroma is fusiform in
shape and is located in the center of a peripheral nerve. The MRI
study is the best diagnostic study for this lesion and shows low
signal abnormality on the T-1 weighted image and demonstrates
5. a very bright, well-marginated spherical lesion on the T-2 weighted
image. Histologically, the neurilemoma has a mixture of dense,
fibrotic, Antoni A substance mixed with a more mucinous Antoni B
substance. In the Antoni A fibrotic tissue, the histological picture is a
palisade of schwann cells and a characteristic and almost diagnostic
Verocay body will be seen demonstrating a palisade of schwann cells
as seen in a Japanese lantern. Treatment for this lesion consists of a
simple blunt dissection of the tumor from a peripheral nerve where
it is located eccentrically and easy to remove without damaging the
subadjacent nerve. The lesion has a characteristic yellow color
contrasting with the white strand-like appearance of the adjacent
nerve. These tumors have a very low recurrence rate and only rarely
will they convert into a malignant schwannoma.
Sometimes the neurilemoma will develop hemorrhagic cystic
changes in patients over the age of 65 years, taking on the appearance
of a hematoma. The lesions can even calcify or form bone as part of a
degenerative process, and are sometimes given the name of ancient
schwannoma in this case.
6. CLASSIC Case #315
Coronal T-1 MRI
gluteus max
55 year male with neurilemoma proximal sciatic nerve
99. Solitary Neurofibroma
The solitary neurofibroma, as opposed to the neurolemoma, is
usually a fusiform, sweet potato shaped peripheral nerve sheath
tumor that arises centrally from the mid-portion of a peripheral nerve.
The lesions are usually small and located in a subcutaneous location.
They are seen between the ages of 20 and 30 years in males and
females equally, and are ten times more common than the neuro-
fibromas seen in Von Reckinghausen’s neurofibromatosis. On MRI,
the lesions are low signal on T-1 and very bright on T-2, and some-
times can be seen arising from a small peripheral nerve. Histo-
logically, the lesions have dense Antoni A substance with palisading
schwann cells, similar to that seen in the neurilemoma. Treatment
consists of simple surgical resection and the recurrence rate is low. A
specific reactive type neurofibroma occurs in the foot between the
third and fourth toes, in the common digital nerve in the web space.
It arises as a result of recurrent compression trauma from wearing
100. tight shoes. This type of neurofibroma, seen typically in females,
can be resected surgically for pain. The so-called amputation
neuroma is a bulbous traumatic neurofibroma seen at the end of
an amputation stump where the peripheral nerves have been
transected during the amputation.
101. CLASSIC Case #322 Sagittal PD MRI
32 year female with neurofibroma foot
130. Neurofibromatosis (Von Recklinghausen’s disease)
Neurofibromatosis is clinically divided into Type I and type II.
Type I involves peripheral nerves and will be discussed in this
section: type II is the central type consisting of acoustic neuroma
that has nothing to do with peripheral neurofibromatosis. The type I
disease is a familial dysplasia, inherited as an autosomal dominant
trait, with an incidence of about one in every 3000 births. The
condition becomes clinically manifest in the first few years of life
with the presence of café-au-laite spots that increase in number and
size over time. Unlike the café-au-laite spots seen in fibrous
dysplasia, the ones in neurofibromatosis have a smooth edge, some-
times referred to as the coast of California. If a patient is found with
more than six lesions with smooth-edged café-au-laite spots greater
than 1-2 cm in diameter, the diagnosis can be made. Later on in life,
the patient will develop numerous cutaneous neurofibromas that
are referred to as fibroma molluscum and have the appearance of
131. small, pedunclated lipomas. The most pathognomic feature of
neurofibromatosis is the large, plexiform neurofibroma associated
with the larger nerves that can involve an entire extremity and can
be associated with loose, hyperpigmented skin that produces an
elephant-like, gross distortion of the skin anatomy referred to as
elephantiasis neuromatosa or elephant man syndrome. Skeletal
deformation can be associated with neurofibromatosis, including
scoliosis (which can be quite angular resulting in paraparesis),
spinal meningoceles, scalloping of vertebral bodies, and pseudo-
arthrosis of the tibia. There can also be associated hypertrophy
or localized gigantism in the hand or foot. As opposed to the
solitary neurofibroma, patients with neurofibromatosis run a 10%
chance of developing a malignant neurofibrosarcoma that usually
occurs during adult life and carries an extremely poor prognosis
for survival.
132. CLASSIC
Case #327
fibroma
molluscum
35 year male type 1
neurofibromatosis with
large plexiform
neurofibroma and
elephantiasis left arm
133. Case #328
11 year male
neurofibromatosis 1
café-au-lait spots &
scoliosis
134. Case #329
Axial T-1 MRI
5 year female with plexiform neurofibromata pelvis
191. Malignant Schwannoma
The malignant schwannoma is a very high grade spindle cell
sarcoma arising from the nerve sheaths of peripheral nerves. It can
arise denovo from a normal appearing peripheral nerve but is more
likely to arise from a solitary neurofibroma. There is a 5 year
survival rate of about 75% in patients over the age of 40 years when
a malignant schwannoma arises from a peripheral solitary neuro-
fibroma. There is a 10% incidence of malignant schwannoma in
patients with neurofibromatosis and the chance for survival at five
years is reduced to 30% and is seen in a younger age group. The
malignant schwannoma is is usually larger than 5 cms and occurs
typically in spinal roots or in the larger proximal nerves such as
the sciatic nerve. The lesions are best picked up by MRI of a painful
mass that occurs in patients with neurofibromatosis and may be
associated with neurological deficits distal to the involved area.
There may also be a café-au-laite spot in the overlying skin. The
192. tumor is usually treated by a wide resection, including the entire
nerve from which it originates, following which local radiation
therapy is recommended to reduce the chance of local recurrence.
Adjuvant chemotherapy is advised even though its benefit is
questionable.
193. CLASSIC
Case #339
tumor
28 year female
malignant schwannoma
sciatic nerve nerve
Sagittal T-2 MRI
245. Granular Cell Tumors
The granular cell tumor is a fairly common soft tissue tumor
that was once thought to be of muscle origin. More recent studies
have proved it to be of neural origin. They are more common in
in males than females and are seen typically in a subcutaneous
location. They are usually painless and less than 3 cm. in
diameter. They are more common in blacks and are seen most
commonly in the fourth thru the sixth decade. By MRI study
the tumors are poorly circumscribed nodular lesions that are low
signal on T-1 and bright on T-2. Histologically the cells have a
benign appearance with a granular appearing cytoplasm. There is
a rare and malignant variant of the granular cell tumor. In the
case of the more common benign form the treatment consists
of simple local excision with little chance of recurrence.
246. Case #1234.1 Axial T-1 Granular cell tumor
T-2 FS
34 year old female with a
painless lump in calf 4 mos
Gad
256. Rhabdomyosarcoma
Rhabdomyosarcoma accounts for 20% of all soft tissue sarcomas.
The embryonal and alveolar types are seen in the pediatric age
group while the less common pleomorphic rhabdomyosarcoma is
seen in adults.
The embryonal rhabdomyosarcoma occurs in children between
the ages of 0 and 15 years, and is seen more commonly in boys
than girls, with the head and neck area being the most common
location for this tumor. Histologically, it is a round cell tumor similar
to Ewing’s sarcoma but in 50% of cases there will be evidence of
cross striation in associated spindle cells and the tumor will have
immunohistochemical markers for desmin, myoglobin, and actin.
Prior to the advent of chemotherapy, this tumor was fatal in about
90% of patients, but with current chemotherapy protocols, patients
survive this tumor in over 80% of cases. Treatment consists of local
surgical resection when indicated, along with postoperative radiation
therapy if the surgical margins are considered contaminated.
257. The alveolar rhabdomyosarcoma affects children between the
ages of 10 and 25 years, and is more commonly seen in males than
females. It occurs in the head and neck area, but can also be seen
in the extremities, especially the thigh and calf. Histologically, this
variant has a typical alveolar pattern of round cells that gives it its
clinical name and only rarely will there be rhabdomyoblasts in the
histological specimens. Treatment consists of surgical resection
followed by radiation therapy if the margins are positive, along
with adjuvant perioperative chemotherapy. The prognosis for
survival is much worse than that of embryonal rhabdomyosarcoma.
The pleomorphic rhabdomyosarcoma is the rarest variant of
the group, consisting of 5% of all cases. It occurs in middle-aged
or older patients and is most commonly located in large muscle
groups in the proximal extremities, usually the lower extremities.
In the 1940’s the pleomorphic rhabdomyosarcoma was a common
histological diagnosis that included many cases of MFH which
at that time was an unpopular histologic diagnosis but a common
258. one by current pathological criteria. Microscopically, this variant
consists of large, bizarre-appearing giant cells with very atypical
nuclei. The cells stain positive for glycogen and cross striations are
frequently seen in the so-called “candy ribbon” cellular patterns
with tandem nuclei on the surface of these rectangular cells. This
variant carries a very poor prognosis for survival and the use of
adjuvant chemotherapy is not nearly as effective as it is for the
pediatric variants. The mainstay of treatment is wide local resection
when possible, followed by radiation therapy, even with negative
surgical margins.
259. CLASSIC Case #345 Axial T-1 MRI
9 month male with embryonal rhabdomyosarcoma pelvis
286. Alveolar Soft Part Sarcoma
The alveolar soft part sarcoma is a high grade round cell sarcoma
affecting patients between the ages of 15 and 35 years, with a pre-
dominance for females. The tumor usually arises from deep muscle
tissue in the lower extremities, most commonly in the thigh. This
tumor is a slow growing lesion that carries a very poor prognosis
because of a high potential for pulmonary metastases. It is felt to
originate from neurogenic stem cells, however, its histological
appearance is similar to that of the alveolar variant of the rhabdo-
myosarcoma which has a similar microscopic appearance. Treatment
usually consists of an attempt at wide surgical resection followed
by postoperative radiation therapy, if the margins are positive, and
chemotherapy because of the high incidence of pulmonary metastases
with an overall survival of approximately 50% at five years.
306. Synovial Sarcoma
The synovial sarcoma is the fourth most common soft tissue
sarcoma seen in the human anatomy. It occurs typically in young
adults between the ages of 15 and 35 years, affecting males slightly
more than females. The name, synovial sarcoma, suggests an
origin in synovial tissue within a major joint. This is a mistaken
concept because only 10% of these tumors will be found inside a
major joint. They usually occur in juxta-articular structures, most
often around the knee, and are frequently associated with tendon
sheaths, bursal sacs, and fascial planes. They can also occur in deep
muscle bellies. These tumors are also commonly seen about the
thigh, shoulder, arm, elbow and wrist area, and are also found about
the foot area. The synovial sarcoma is unusual in that it usually
starts off with a very slow growth pattern that may suggest a benign
process masquerading as an injury to the extremities. In many cases
there is dystrophic calcification or even heterotopic bone within the
tumor, again suggesting a benign diagnosis that clinicians may
307. inject for symptomatic relief.
Microscopically, this tumor has a characteristic biphasic pattern
with a combination of epithelioid-looking cells that form in nests,
clefts, or even in a tubular structure formation associated with
malignant-appearing spindle cells in the same area. There is a
monophasic form of this sarcoma, usually a spindle cell form, that
has the appearance of a fibrosarcoma. There is also an epithelioid
form of the synovial sarcoma that is quite unusual. Despite the
benign clinical appearance of the tumor, the prognosis for survival
is very poor, with only about 50% of patients surviving for five
years and only 25% surviving ten years. There is a high (20%)
metastatic involvement of proximal lymph nodes that should be
looked for and treated by aggressive resection and local radiation
therapy. In about 30% of cases, there will be heavy calcification
within the tumor that indicates a more benign prognosis with an
80% survival rate at five years in this group.
The treatment for this tumor consists of wide local resection,
308. if possible, or high level amputation for cases where local control
is difficult. Following a wide resection, local radiation therapy is
employed. If the prognosis seems extremely guarded, chemo-
therapy is indicated.
309. CLASSIC Case #354
20 year female with synovial sarcoma shoulder
