Neurilemoma The neurilemoma, sometimes referred to as a benign schwanoma,is a nerve sheath tumor arising from the schwann cell surroundingthe axons of peripheral nerves. It affects individuals between theages of 20 and 50 years and occurs equally in males and females. Itis 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 neurofibromatosismultiple lesions may occur. These benign lesions are slow growingand very rarely cause neurological symptoms or defect becauseof their benign behavior. As opposed to the more common neuro-fibroma, the neurilemoma is typically a round structure attached tothe periphery of a nerve whereas the neurofibroma is fusiform inshape and is located in the center of a peripheral nerve. The MRIstudy is the best diagnostic study for this lesion and shows lowsignal abnormality on the T-1 weighted image and demonstrates
a very bright, well-marginated spherical lesion on the T-2 weightedimage. Histologically, the neurilemoma has a mixture of dense,fibrotic, Antoni A substance mixed with a more mucinous Antoni Bsubstance. In the Antoni A fibrotic tissue, the histological picture is apalisade of schwann cells and a characteristic and almost diagnosticVerocay body will be seen demonstrating a palisade of schwann cellsas seen in a Japanese lantern. Treatment for this lesion consists of asimple blunt dissection of the tumor from a peripheral nerve whereit is located eccentrically and easy to remove without damaging thesubadjacent nerve. The lesion has a characteristic yellow colorcontrasting with the white strand-like appearance of the adjacentnerve. These tumors have a very low recurrence rate and only rarelywill they convert into a malignant schwannoma. Sometimes the neurilemoma will develop hemorrhagic cysticchanges in patients over the age of 65 years, taking on the appearanceof a hematoma. The lesions can even calcify or form bone as part of adegenerative process, and are sometimes given the name of ancientschwannoma in this case.
CLASSIC Case #315 Coronal T-1 MRI gluteus max 55 year male with neurilemoma proximal sciatic nerve
Solitary Neurofibroma The solitary neurofibroma, as opposed to the neurolemoma, isusually a fusiform, sweet potato shaped peripheral nerve sheathtumor 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 andfemales 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 palisadingschwann cells, similar to that seen in the neurilemoma. Treatmentconsists of simple surgical resection and the recurrence rate is low. Aspecific reactive type neurofibroma occurs in the foot between thethird and fourth toes, in the common digital nerve in the web space.It arises as a result of recurrent compression trauma from wearing
tight shoes. This type of neurofibroma, seen typically in females,can be resected surgically for pain. The so-called amputationneuroma is a bulbous traumatic neurofibroma seen at the end ofan amputation stump where the peripheral nerves have beentransected during the amputation.
CLASSIC Case #322 Sagittal PD MRI 32 year female with neurofibroma foot
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
small, pedunclated lipomas. The most pathognomic feature ofneurofibromatosis is the large, plexiform neurofibroma associatedwith the larger nerves that can involve an entire extremity and canbe associated with loose, hyperpigmented skin that produces anelephant-like, gross distortion of the skin anatomy referred to aselephantiasis neuromatosa or elephant man syndrome. Skeletaldeformation can be associated with neurofibromatosis, includingscoliosis (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 hypertrophyor localized gigantism in the hand or foot. As opposed to thesolitary neurofibroma, patients with neurofibromatosis run a 10%chance of developing a malignant neurofibrosarcoma that usuallyoccurs during adult life and carries an extremely poor prognosisfor survival.
CLASSICCase #327 fibroma molluscum35 year male type 1neurofibromatosis withlarge plexiformneurofibroma andelephantiasis left arm
Case #32811 year maleneurofibromatosis 1café-au-lait spots &scoliosis
Case #329 Axial T-1 MRI 5 year female with plexiform neurofibromata pelvis
Malignant Schwannoma The malignant schwannoma is a very high grade spindle cellsarcoma arising from the nerve sheaths of peripheral nerves. It canarise denovo from a normal appearing peripheral nerve but is morelikely to arise from a solitary neurofibroma. There is a 5 yearsurvival rate of about 75% in patients over the age of 40 years whena malignant schwannoma arises from a peripheral solitary neuro-fibroma. There is a 10% incidence of malignant schwannoma inpatients with neurofibromatosis and the chance for survival at fiveyears is reduced to 30% and is seen in a younger age group. Themalignant schwannoma is is usually larger than 5 cms and occurstypically in spinal roots or in the larger proximal nerves such asthe sciatic nerve. The lesions are best picked up by MRI of a painfulmass that occurs in patients with neurofibromatosis and may beassociated with neurological deficits distal to the involved area.There may also be a café-au-laite spot in the overlying skin. The
tumor is usually treated by a wide resection, including the entirenerve from which it originates, following which local radiationtherapy is recommended to reduce the chance of local recurrence.Adjuvant chemotherapy is advised even though its benefit isquestionable.
Granular Cell Tumors The granular cell tumor is a fairly common soft tissue tumorthat was once thought to be of muscle origin. More recent studieshave proved it to be of neural origin. They are more common inin males than females and are seen typically in a subcutaneouslocation. They are usually painless and less than 3 cm. indiameter. They are more common in blacks and are seen mostcommonly in the fourth thru the sixth decade. By MRI studythe tumors are poorly circumscribed nodular lesions that are lowsignal on T-1 and bright on T-2. Histologically the cells have abenign appearance with a granular appearing cytoplasm. There isa rare and malignant variant of the granular cell tumor. In thecase of the more common benign form the treatment consistsof simple local excision with little chance of recurrence.
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
Rhabdomyosarcoma Rhabdomyosarcoma accounts for 20% of all soft tissue sarcomas.The embryonal and alveolar types are seen in the pediatric agegroup while the less common pleomorphic rhabdomyosarcoma isseen in adults. The embryonal rhabdomyosarcoma occurs in children betweenthe ages of 0 and 15 years, and is seen more commonly in boysthan girls, with the head and neck area being the most commonlocation for this tumor. Histologically, it is a round cell tumor similarto Ewing’s sarcoma but in 50% of cases there will be evidence ofcross striation in associated spindle cells and the tumor will haveimmunohistochemical markers for desmin, myoglobin, and actin.Prior to the advent of chemotherapy, this tumor was fatal in about90% of patients, but with current chemotherapy protocols, patientssurvive this tumor in over 80% of cases. Treatment consists of localsurgical resection when indicated, along with postoperative radiationtherapy if the surgical margins are considered contaminated.
The alveolar rhabdomyosarcoma affects children between theages of 10 and 25 years, and is more commonly seen in males thanfemales. It occurs in the head and neck area, but can also be seenin the extremities, especially the thigh and calf. Histologically, thisvariant has a typical alveolar pattern of round cells that gives it itsclinical name and only rarely will there be rhabdomyoblasts in thehistological specimens. Treatment consists of surgical resectionfollowed by radiation therapy if the margins are positive, alongwith adjuvant perioperative chemotherapy. The prognosis forsurvival is much worse than that of embryonal rhabdomyosarcoma. The pleomorphic rhabdomyosarcoma is the rarest variant ofthe group, consisting of 5% of all cases. It occurs in middle-agedor older patients and is most commonly located in large musclegroups in the proximal extremities, usually the lower extremities.In the 1940’s the pleomorphic rhabdomyosarcoma was a commonhistological diagnosis that included many cases of MFH whichat that time was an unpopular histologic diagnosis but a common
one by current pathological criteria. Microscopically, this variantconsists of large, bizarre-appearing giant cells with very atypicalnuclei. The cells stain positive for glycogen and cross striations arefrequently seen in the so-called “candy ribbon” cellular patternswith tandem nuclei on the surface of these rectangular cells. Thisvariant carries a very poor prognosis for survival and the use ofadjuvant chemotherapy is not nearly as effective as it is for thepediatric variants. The mainstay of treatment is wide local resectionwhen possible, followed by radiation therapy, even with negativesurgical margins.
CLASSIC Case #345 Axial T-1 MRI 9 month male with embryonal rhabdomyosarcoma pelvis
Alveolar Soft Part Sarcoma The alveolar soft part sarcoma is a high grade round cell sarcomaaffecting patients between the ages of 15 and 35 years, with a pre-dominance for females. The tumor usually arises from deep muscletissue in the lower extremities, most commonly in the thigh. Thistumor is a slow growing lesion that carries a very poor prognosisbecause of a high potential for pulmonary metastases. It is felt tooriginate from neurogenic stem cells, however, its histologicalappearance is similar to that of the alveolar variant of the rhabdo-myosarcoma which has a similar microscopic appearance. Treatmentusually consists of an attempt at wide surgical resection followedby postoperative radiation therapy, if the margins are positive, andchemotherapy because of the high incidence of pulmonary metastaseswith an overall survival of approximately 50% at five years.
CLASSICCase #35022 year femalealveolar soft partsarcoma pelvis
Synovial Sarcoma The synovial sarcoma is the fourth most common soft tissuesarcoma seen in the human anatomy. It occurs typically in youngadults between the ages of 15 and 35 years, affecting males slightlymore than females. The name, synovial sarcoma, suggests anorigin in synovial tissue within a major joint. This is a mistakenconcept because only 10% of these tumors will be found inside amajor joint. They usually occur in juxta-articular structures, mostoften around the knee, and are frequently associated with tendonsheaths, bursal sacs, and fascial planes. They can also occur in deepmuscle bellies. These tumors are also commonly seen about thethigh, shoulder, arm, elbow and wrist area, and are also found aboutthe foot area. The synovial sarcoma is unusual in that it usuallystarts off with a very slow growth pattern that may suggest a benignprocess masquerading as an injury to the extremities. In many casesthere is dystrophic calcification or even heterotopic bone within thetumor, again suggesting a benign diagnosis that clinicians may
inject for symptomatic relief. Microscopically, this tumor has a characteristic biphasic patternwith a combination of epithelioid-looking cells that form in nests,clefts, or even in a tubular structure formation associated withmalignant-appearing spindle cells in the same area. There is amonophasic form of this sarcoma, usually a spindle cell form, thathas the appearance of a fibrosarcoma. There is also an epithelioidform of the synovial sarcoma that is quite unusual. Despite thebenign clinical appearance of the tumor, the prognosis for survivalis very poor, with only about 50% of patients surviving for fiveyears and only 25% surviving ten years. There is a high (20%)metastatic involvement of proximal lymph nodes that should belooked for and treated by aggressive resection and local radiationtherapy. In about 30% of cases, there will be heavy calcificationwithin the tumor that indicates a more benign prognosis with an80% survival rate at five years in this group. The treatment for this tumor consists of wide local resection,
if possible, or high level amputation for cases where local controlis difficult. Following a wide resection, local radiation therapy isemployed. If the prognosis seems extremely guarded, chemo-therapy is indicated.
CLASSIC Case #354 20 year female with synovial sarcoma shoulder